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Using Claude for Excel with Hemrock models

Claude for Excel gives you an AI that reads and edits your spreadsheet directly. Pair it with a Hemrock model and you're editing proven structure, not generating from scratch.

Claude for Excel is Anthropic's Excel add-in. It reads your workbook, answers questions about cells and formulas, and makes edits in place.

Hemrock models are built to edit. Every cell is open, every formula is documented, and the structure is already proven. Claude for Excel lets you customize that structure in plain English, without rebuilding the plumbing yourself.

Why this pairing works

You start with a model that already balances, already flows, and already handles the edge cases. Claude sees the full workbook: blue inputs, black formulas, named ranges, notes. You describe the change, Claude proposes edits, and you review before it writes. Your structure stays intact while you shape it to your business.

Install it

Install the Claude for Excel add-in from Anthropic. See the current install steps and plan requirements at anthropic.com/claude/excel.

Set it up for a Hemrock model

Before you ask Claude to touch anything, paste two things into the chat:

1. The universal context primer. Tells Claude how every Hemrock model is structured.

I am working on a Hemrock (formerly Foresight) financial model template created by Taylor Davidson (hemrock.com, formerly foresight.is). Before we start, here is how these models are structured:

FORMATTING CONVENTIONS:
- Blue font with light grey background = an input cell (assumption you can change). Only edit these.
- Black font = a formula or calculation. Do not modify these unless you fully understand the formula and its downstream effects.
- All cells and formulas are unlocked. There are no macros.
- Many cells have notes explaining what they do. Read them before changing anything.

SHEET STRUCTURE:
- README / License / Disclaimer: Informational only. Safe to ignore or hide.
- Get Started: Top-level model inputs and settings. Start here.
- Forecast: Detailed assumptions and inputs. A hybrid inputs-and-calculations sheet. Treat blue cells as inputs, black cells as hands-off.
- Revenues: Revenue model calculations (Standard Model). Driven by inputs on Get Started and Forecast.
- Statements: Consolidated financial statements (income statement, balance sheet, cash flow).
- Summary / Key Reports / Breakdown / Budget / Sources and Uses: Presentation and analysis sheets. Output only. Do not manually edit.
- Changelog: Version history. Do not delete.

CORE PRINCIPLES:
- Inputs, calculations, and presentations are intentionally separated. Never hard-code values into calculation or presentation sheets.
- All current assumptions are illustrative only. They are not market data or standards.
- The model is designed to be used iteratively, not as a static output.
- When in doubt, ask which cells are inputs before suggesting changes.

BEFORE MAKING ANY CHANGES:
1. Confirm with me which cells are blue (inputs) vs. black (calculations).
2. Tell me what downstream effects your proposed change will have.
3. Do not hard-code values into formula cells.
4. If a change requires modifying a formula, explain exactly what you are changing and why.

2. The model-specific primer. Grab it from /docs/ai for whichever model you're in (Standard Financial Model, Venture Capital Model, Cap Table & Exit Waterfall, and others).

Or skip the paste entirely: connect the Hemrock MCP server (mcp.hemrock.com) and Claude will pull primers, task prompts, and sanity checks automatically.

Editing pattern

Every change, every time. Ask which cells are blue vs. black before editing: blue is yours, black is load-bearing. Never hard-code a number into a calculation row; if it needs to be an assumption, move it to Get Started or a blue cell on Forecast. Demand a downstream-effects summary before Claude writes. What other sheets change when you edit this? Spot-check the result: does Statements still balance, did Summary update, did a driver break? Keep one change per turn. Compounding edits compound bugs.

Rules

Blue cells in, inputs only. Black cells out, formulas only. Verify every AI edit. AI is fast, not infallible. Skipping verification is the one thing we tell founders never to do, and it applies here too.