Experimenting with skills for Copilot For Excel

Microsoft has developed a new skill for Copilot for Excel that automates the creation of structured LAMBDA functions following 5th Generation Modeling standards. The skill guides users through an eight-step workflow to convert formulas into documented, reusable LAMBDA functions with inline help, parameter handling, and automatic testing. This integration brings professional-grade function development practices directly into Excel's AI assistant.

| 5G LAMBDA Template Skill | | | Version: 1.4 | | | Last Updated: May-20-2026 | | | skill: | | | name: lambda-template-5g | | | description: | | | Rules and conventions for creating well-structured Excel LAMBDA functions | | | with inline help documentation using the Advanced Formula Environment AFE . | | | Follows 5th Generation Modeling standards from 5gmodelling.com. | | | category: Excel | | | tags: | | | - LAMBDA | | | - AFE | | | - Excel Labs | | | - Named Functions | | | - Documentation | | | - 5G Modeling | | | ═══════════════════════════════════════════════════════════════════════════ | | | TRIGGER PHRASES | | | ═══════════════════════════════════════════════════════════════════════════ | | | triggers: | | | - "Make 5g" | | | - "Make LAMBDA" | | | - "Convert to 5g" | | | - "Convert to LAMBDA" | | | ═══════════════════════════════════════════════════════════════════════════ | | | WORKFLOW | | | ═══════════════════════════════════════════════════════════════════════════ | | | workflow: | | | description: | | | Step-by-step process to convert a formula into a 5G LAMBDA function. | | | Do not scan the workbook before taking step 1. | | | steps: | | | - step: 1 | | | action: Ask for user's name | | | prompt: "What name shall I use for version control?" | | | usage: Used in REVISIONS section and VERSION line | | | - step: 2 | | | action: Ask for formula | | | prompt: "Select formulas to convert into a 5G LAMBDA function." | | | usage: Identifies parameters and core logic | | | - step: 3 | | | action: Display parameters and ask if any are optional | | | prompt: "Are any of these inputs optional? If yes, which ones and what is each optional parameter's default value?" | | | usage: Determines bracket conventions and default value logic | | | - step: 4 | | | action: Display suggested function names and ask for function name | | | prompt: "What would you like to name this function? e.g., MonthlyPaymentλ " | | | usage: Used throughout the LAMBDA definition and help text | | | - step: 5 | | | action: Add to names collection | | | description: Add the 5G LAMBDA function to the workbook's names collection | | | - step: 6 | | | action: Test the function | | | description: Find an empty space below the original example and run the 5g function with the same inputs as the original example. | | | Leave the test results for the user to examine. Do not clean them up. | | | - step: 7 | | | action: Compare results | | | description: Compare the 5G function's output to the original example to verify correctness | | | - step: 8 | | | action: Display Source | | | description: Write the fully commented source to the chat window. Use TEMPLATE STRUCTURE as a guide. | | | ═══════════════════════════════════════════════════════════════════════════ | | | RULES | | | ═══════════════════════════════════════════════════════════════════════════ | | | rules: | | | ───────────────────────────────────────────────────────────────────────── | | | 1. PLACEHOLDER BRACKETS | | | ───────────────────────────────────────────────────────────────────────── | | | placeholder brackets: | | | description: | | | Template placeholders like <description are instructional only. | | | Remove the angle brackets < in the generated output. | | | example: | | | template: "<Calculates the monthly payment " | | | output: "Calculates the monthly payment" | | | ───────────────────────────────────────────────────────────────────────── | | | 2. USER NAME | | | ───────────────────────────────────────────────────────────────────────── | | | user name: | | | description: | | | Always ask for the user's name at the start of the workflow. | | | Use it in the REVISIONS section and VERSION line. | | | prompt: "What is your name?" | | | ───────────────────────────────────────────────────────────────────────── | | | 3. DATE HANDLING | | | ───────────────────────────────────────────────────────────────────────── | | | date handling: | | | description: | | | Use the current date for the REVISIONS section and VERSION line. | | | format: "Mmm-dd-yyyy" | | | example: "May-15-2026" | | | ───────────────────────────────────────────────────────────────────────── | | | 4. OPTIONAL PARAMETERS | | | ───────────────────────────────────────────────────────────────────────── | | | optional parameters: | | | description: | | | Ask if any inputs are optional. If yes, ask which ones and | | | what each optional parameter's default value is. | | | prompt: "Are any of these inputs optional? If yes, which ones and what is each optional parameter's default value?" | | | handling: | | | lambda definition: "All arguments use brackets " | | | help text function line: | | | required: "NO brackets e.g., Amount " | | | optional: "WITH brackets e.g., Term " | | | help text parameters: | | | required: " Required description" | | | optional: " Optional Default: value. description" | | | let section: | | | Add default value assignment for optional params: | | | ParamName, IF ISOMITTED ParamName , DefaultValue, ParamName , | | | ───────────────────────────────────────────────────────────────────────── | | | 5. ARGUMENT BRACKETS CONVENTION | | | ───────────────────────────────────────────────────────────────────────── | | | argument brackets: | | | description: | | | All arguments must appear optional to Excel so help text can display | | | when required arguments are omitted. The help text signals which are | | | truly required by omitting brackets. | | | lambda definition: | | | required: " Argument " | | | optional: " Argument " | | | help text function line: | | | required: "ARGUMENT" | | | optional: " Argument " | | | ───────────────────────────────────────────────────────────────────────── | | | 6. TEXTSPLIT DELIMITERS | | | ───────────────────────────────────────────────────────────────────────── | | | textsplit delimiters: | | | description: | | | TEXTSPLIT creates a formatted help table that displays | | | in the Excel grid when required arguments are omitted. | | | syntax: 'TEXTSPLIT text, "→", "¶" ' | | | delimiters: | | | column: "→" | | | row: "¶" | | | ───────────────────────────────────────────────────────────────────────── | | | 7. MULTI-ROW PARAMETER DESCRIPTIONS | | | ───────────────────────────────────────────────────────────────────────── | | | multi row descriptions: | | | description: | | | When a parameter description needs multiple rows in the grid display, | | | use a leading "→" on continuation lines for proper column alignment. | | | example: | | | | " PositiveOnly? → Optional TRUE: Outflows are entered as positive values ¶" & | | | "→ that this function will subtract from the opening balance. ¶" & | | | "→ FALSE: Outflows are entered as negative values. Default is FALSE." | | | ───────────────────────────────────────────────────────────────────────── | | | 8. LET STEP RESULTS | | | ───────────────────────────────────────────────────────────────────────── | | | let step results: | | | description: | | | Name the last calculation in the LET Function. | | | Use that name as the last step in the LET function. | | | ───────────────────────────────────────────────────────────────────────── | | | 9. EXCEL SYNTAX RULES | | | ───────────────────────────────────────────────────────────────────────── | | | excel syntax: | | | description: | | | Follow standard Excel conventions for function names and booleans. | | | booleans: "Uppercase: FALSE, TRUE" | | | function names: "Uppercase: AVERAGE , INDEX , SCAN , REDUCE , PMT " | | | ───────────────────────────────────────────────────────────────────────── | | | 10. STRING CONCATENATION | | | ───────────────────────────────────────────────────────────────────────── | | | string concatenation: | | | description: | | | Ensure all help text lines are properly concatenated with the & operator. | | | rule: "Every line except the last must end with &" | | | ───────────────────────────────────────────────────────────────────────── | | | 11. INDEX BEHAVIOR | | | ───────────────────────────────────────────────────────────────────────── | | | index behavior: | | | description: | | | When working with single-row arrays, INDEX interprets the second | | | argument as the column number. | | | rule: "When array is a single row, INDEX array, n returns the nth column value" | | | ───────────────────────────────────────────────────────────────────────── | | | 12. MULTIPLE FORMULAS | | | ───────────────────────────────────────────────────────────────────────── | | | multiple formulas: | | | description: | | | When the user selects multiple cells containing formulas, | | | include all of them in the LAMBDA function. | | | handling: | | | - Identify all formulas in the selected range | | | - Combine them logically within a single LAMBDA | | | - Create appropriate parameters for all unique inputs across formulas | | | - Document each formula's purpose in the help text | | | ───────────────────────────────────────────────────────────────────────── | | | 13. INPUT CELL DETECTION | | | ───────────────────────────────────────────────────────────────────────── | | | input cell detection: | | | description: | | | When formulas reference cells outside the selected range, determine | | | which cells become LAMBDA inputs based on their content. | | | rules: | | | - If a referenced cell contains a value not a formula , it becomes an input | | | - If a referenced cell contains a formula that only references another cell | | | passthrough , follow the reference chain to find the true input | | | - If a referenced cell contains a formula with calculations, that cell | | | itself becomes an input | | | example: | | | scenario: "Selected formula references B5, and B5 contains =C3" | | | result: "C3 becomes the input, not B5 B5 is a passthrough " | | | ───────────────────────────────────────────────────────────────────────── | | | 14. HORIZONTAL SEQUENCE FOR SCAN | | | ───────────────────────────────────────────────────────────────────────── | | | horizontal sequence scan: | | | description: | | | When using SCAN to build a horizontal array, use SEQUENCE 1, n | | | instead of SEQUENCE n to avoid needing TRANSPOSE afterward. | | | rule: "SEQUENCE 1, Term produces horizontal output directly from SCAN" | | | example: | | | inefficient: | | | | CloseBal, SCAN Amount, SEQUENCE Term , LAMBDA bal, n, formula , | | | CloseRow, TRANSPOSE CloseBal , | | | elegant: | | | | CloseBal, SCAN Amount, SEQUENCE 1, Term , LAMBDA bal, n, formula , | | | ───────────────────────────────────────────────────────────────────────── | | | 15. DROP VS TAKE FOR ARRAY SLICING | | | ───────────────────────────────────────────────────────────────────────── | | | drop vs take: | | | description: | | | When removing elements from the end of an array, prefer DROP over TAKE | | | to avoid referencing array length variables. | | | rule: "Use DROP array, , -1 instead of TAKE array, 1, Length-1 " | | | example: | | | inefficient: "OpenBal, HSTACK Amount, TAKE CloseBal, 1, Term-1 " | | | elegant: "OpenBal, HSTACK Amount, DROP CloseBal, , -1 " | | | ───────────────────────────────────────────────────────────────────────── | | | 16. FIXED RANGE ARGUMENTS | | | ───────────────────────────────────────────────────────────────────────── | | | fixed range arguments: | | | description: | | | Convert arguments that cover multiple columns to arrays | | | rule: "Determine which argument sets the number of columns columns in the result. | | | Expand multi-cell, fixed range arguments argument using EXPAND argument, 1, columns, 0 ." | | | purpose: "Makes sure argument sizes remain dynamic ad agree with other array sizes." | | | ───────────────────────────────────────────────────────────────────────── | | | 17. MATCH EXAMPLE OUTPUT | | | ───────────────────────────────────────────────────────────────────────── | | | match example output: | | | description: | | | match the function's output to the example's output | | | rule: "Include in the function's output all selected formula rows. Copy formats from the example to the output." | | | purpose: "Keep the users desired output." | | | ═══════════════════════════════════════════════════════════════════════════ | | | TEMPLATE STRUCTURE | | | ═══════════════════════════════════════════════════════════════════════════ | | | template: | | | description: | | | Standard structure for 5G LAMBDA functions with inline documentation. | | | code: | | | | / FUNCTION NAME: Functionλ | | | DESCRIPTION: // Description of what the function does / | | | / REVISIONS: Date Developer Description | | | Mmm dd yyyy UserName Copyright/Initial Release | | | / | | | Functionλ = LAMBDA | | | // Function Arguments | | | Required1 , // Description | | | Required2 , // Description | | | Optional1 , // Description default: value | | | // Check required arguments | | | IF OR ISOMITTED Required1 , | | | ISOMITTED Required2 | | | , | | | // Display inline help text | | | TRIM TEXTSPLIT | | | "FUNCTION: →Functionλ Required1, Required2, Optional1 ¶" & | | | "DESCRIPTION: →Description of what the function does¶" & | | | "WEBPAGE: →https://5gmodelling.com¶" & | | | "VERSION: →UserName, Mmm-dd-yyyy¶" & | | | "PARAMETERS: →¶" & | | | " Required1 → Required Description¶" & | | | " Required2 → Required Description¶" & | | | " Optional1 → Optional Default: value. Description", | | | "→", "¶" , | | | // Main function logic | | | LET | | | // Set Defaults | | | Optional1, IF ISOMITTED Optional1 , DefaultValue, Optional1 , | | | // Calculations | | | Result, formula, | | | Result | | | | | | | | | ; | | | ═══════════════════════════════════════════════════════════════════════════ | | | CHECKLIST | | | ═══════════════════════════════════════════════════════════════════════════ | | | checklist: | | | - "Function name matches throughout definition, help text FUNCTION line " | | | - "All brackets correct in LAMBDA definition Argument " | | | - "Help text FUNCTION line: required args NO brackets, optional args WITH brackets" | | | - "All & concatenation operators present between help text lines" | | | - "TEXTSPLIT delimiters correct: \"→\", \"¶\" column, row " | | | - "All parentheses balanced TEXTSPLIT, TRIM, IF, LET, LAMBDA " | | | - "Boolean values uppercase: FALSE, TRUE" | | | - "Function names uppercase: AVERAGE, INDEX, SCAN, REDUCE" | | | - "Multi-row descriptions use leading \"→\" for continuation lines" | | | - "Optional params have default value logic in LET section" | | | - "User's name appears in REVISIONS and VERSION" | | | - "Current date used in REVISIONS and VERSION" | | | - "No angle brackets < in final output" | | | - "If multiple formulas selected, all are included in the LAMBDA" | | | - "Follow input cell detection rules for passthrough references" | | | - "Use SEQUENCE 1, n for horizontal arrays in SCAN operations" | | | - "Prefer DROP over TAKE when removing elements from array" |