AI for Excel VBA: Write and Test Workbook Macros

Use AI for Excel VBA by specifying one repeatable workbook task, requesting a readable macro, and reviewing and testing the code on a copy before running it on working data. VBA, or Visual Basic for Applications, is the programming language used for these Excel macros. Generated code still needs someone to confirm what it reads, changes, and leaves behind.

Tools like fenbs keep the approved prompt, constraints, and lessons from failed tests available across assistants. That record helps when next month’s workbook is slightly different or another person takes over the macro.

What is the practical workflow for an AI-written macro?

1. Choose one narrow task and write its expected result. Decide whether a formula or built-in Excel feature could do it more simply.
2. Describe the workbook, sheets, headers, and permitted changes. Use invented sample data rather than sharing confidential rows.
3. Ask the AI to explain a plan before generating VBA. Resolve missing requirements and request code that fails clearly when the workbook does not match.
4. Review the code and its side effects with someone who understands VBA. Test on a separate workbook copy with known inputs and expected outputs.
5. Keep the reviewed code, tests, and original workbook recoverable. Approve a working run only when its checks match the agreed specification.

AI coding tools can help explain, draft, and review code; OpenAI describes those uses in its code generation guide↗ (opens in a new tab). The workflow here adds the Excel-specific checks that a generated explanation alone cannot provide. For cell calculations rather than macros, use our AI formula guide.

How should you describe the workbook task?

“Clean my workbook” is too broad. Say which sheet contains input, how records are identified, and exactly where the output goes. Define whether the macro may overwrite cells, create sheets, remove rows, or save the file. A missing instruction can become an unintended action.

Consider a practice task: copy numeric sales records from an Input sheet into a separate Review sheet. Decide what counts as numeric, whether blanks should be reported, and what happens if Review already exists. A useful default is to stop and explain the conflict rather than overwrite earlier work.

Draft an Excel desktop VBA macro for a practice workbook.
Input sheet: Input. Row 1 headers: ID, Region, Amount. Data is A2:C20.
Create a sheet named Review and copy values for rows with numeric Amount.
Report skipped rows; do not silently convert text to numbers.
If Input is missing or Review already exists, stop without changes.
Do not delete, overwrite source data, save, send email, or access files or networks.
Use explicit workbook and worksheet references and Option Explicit.
First explain the plan, assumptions, failure behavior, and test cases.
Then provide commented VBA and instructions for reviewing it.

Keep the fixed practice range explicit. If the real workbook needs a growing table, describe that separately and test it separately. A prompt that changes from a fixed range to “all rows” has changed the specification, even if the macro name stays the same.

Save the reviewed prompt and its permitted changes in fenbs Skills and prompts. Reusing the complete request is more dependable than remembering only the last sentence you typed.

What should you look for in the generated VBA?

Read from the entry point to every operation that changes something. Ask for plain-English explanations of unfamiliar statements, then verify them in Microsoft’s documentation. If you cannot explain the macro’s effects, get a qualified reviewer before enabling it.

Check workbook and worksheet references closely. Microsoft’s Range object documentation↗ (opens in a new tab) explains that an unqualified Range reference uses the active sheet. That makes code dependent on what happens to be selected. Prefer an explicit target and test what happens when a different sheet is active.

• Scope: every read and write stays within the approved workbook, sheets, and ranges.
• Destructive operations: deletion, clearing, overwriting, and saving are absent unless specifically required and reviewed.
• Outside actions: file access, shell commands, network requests, and messages are absent unless part of an explicitly approved design.
• Failure behavior: missing sheets, invalid values, and existing output cause the agreed response.
• Cleanup: any settings the code changes are restored on both success and failure.

How do you test without risking the real workbook?

Make a separate test copy and keep an unchanged baseline to compare afterward. Begin with a tiny dataset whose output you can predict by hand. Record the number of accepted rows, rejected rows, and output cells, rather than judging success by the absence of an error message.

Run the tests again after each code change. Include a test with another workbook open and another sheet selected. If the macro has more complex effects than this small example, expand the test plan before expanding its permissions.

What should you do about macro security and recovery?

Use your organization’s approved process for enabling reviewed macros. Microsoft’s macro security guidance↗ (opens in a new tab) explains that macros can run harmful code and that administrators may restrict settings. Do not disable broad security protections just because an AI-generated macro will not run.

Plan recovery before execution. Keep the original file outside the test workflow, and know which copy you will restore if a check fails. Do not assume a normal undo action can reverse every effect of a macro, especially if it saves files or changes something outside the workbook.

For repeated team use, name a maintainer and define when review is required again. A changed header, new input sheet, or different reporting rule can invalidate earlier tests. Our AI at work guide covers choosing bounded tasks, while what an AI brain keeps explains the value of retaining the work record. More examples are in the AI at work hub.

How to do this with fenbs

1. Create a free account and add a project for the workbook process.
2. Save the reviewed request in Skills and prompts and record the human-approved constraints in Decisions and rules.
3. Add a test task with the expected outputs, actual results, and remaining checks. Keep the workbook and macro source in their approved storage location.
4. Record what a failed run taught you in Lessons learned, then save Where we left off so the next connected assistant knows which version still needs review.

fenbs is free for one person, no credit card. It does not execute VBA or test a workbook for you. If you need an Excel automation runtime, use the appropriate spreadsheet tooling; fenbs fits the reusable instructions, review tasks, and continuity around that work.