Spreadsheet formula helper for Excel and Google Sheets that asks for your layout before writing a formula
A portable assistant for anyone working in Excel or Google Sheets: describe what you need and your column layout, and it writes the formula for your app and version, explains each part, lists edge cases, and gives a test row to check it.
Agent in Data by AISkillHub Library
What it does
Most formula answers fail because they assume a layout, or use a function your spreadsheet app does not have. This assistant asks which app you use and how your data is laid out, then writes a formula that fits, with a plain explanation and a quick way to test it.
**What it does**
- Asks three things up front if you did not say: Excel or Google Sheets (and for Excel, Microsoft 365 or an older version), the sheet layout (headers and example rows), and where the result should go. - Writes the formula with your real ranges and sheet names. - Prefers functions available in your app: for example XLOOKUP, FILTER and LET in Microsoft 365 and Google Sheets; INDEX/MATCH for older Excel; QUERY and ARRAYFORMULA only in Google Sheets. - Explains the formula part by part. - Lists edge cases (blanks, text stored as numbers, duplicates, errors) and how the formula handles them, with a wrapped version if needed. - Gives a small test table with expected results so you can check it before filling down. - Also debugs: paste a formula and the error or wrong result and it finds the cause.
**When to use it**
- Lookups across sheets, conditional sums and counts, date math, text cleanup, deduplication, ranking - Converting a formula between Excel and Google Sheets - Understanding an inherited spreadsheet
**What it will not do**
- It does not write VBA macros or Apps Script unless you ask, and then it says so clearly because scripts run with your permissions. - It does not see your file. If it guesses your layout, it says what it assumed. - It does not give accounting or tax advice. It writes the formula for the rule you give it.
**Example**
Request: "Sum column D where column B is 'Paid' and the date in column A is in March 2026. Google Sheets, headers in row 1."
Answer: `=SUMIFS(D2:D, B2:B, "Paid", A2:A, ">="&DATE(2026,3,1), A2:A, "<"&DATE(2026,4,1))`, an explanation of each condition, a note that dates stored as text will be skipped and how to check with `ISNUMBER(A2)`, and a four-row test table.
How to use it
The same `assistants/spreadsheet-formula-helper/instructions.md` works in all three products. Pick one:
- **ChatGPT custom GPT:** Explore GPTs, then **Create**, then the **Configure** tab. Name it `Formula Helper` and paste the file into **Instructions**. Upload (optional) a CSV export of the first 20 rows of a sheet you work with often, with sensitive data removed, so the assistant can use your real column names in the product's file or knowledge area. - **Claude Project:** create a project named `Formula Helper`, paste the file into the project's custom instructions setting. Upload (optional) a CSV export of the first 20 rows of a sheet you work with often, with sensitive data removed, so the assistant can use your real column names in the product's file or knowledge area. - **Gemini Gem:** in the Gems manager create a **New Gem** named `Formula Helper` and paste the file into **Instructions**. Upload (optional) a CSV export of the first 20 rows of a sheet you work with often, with sensitive data removed, so the assistant can use your real column names in the product's file or knowledge area. - **No setup option:** paste the whole file as the first message of a new chat in any of the three, then continue in that chat.
**Variables to fill before pasting:** `{{default_app}}` in the file can be set to `Excel 365`, `Excel 2019`, or `Google Sheets` so it stops asking. Leave it as is to be asked each time. Your decimal and list separator matter: if your locale uses commas for decimals, say so and the assistant uses semicolons as argument separators.
Test with one real example before sharing it with your team.
Files
Save each file at the path shown, relative to your project root.