An Excel add-in that treats AI like just another formula

What it does Cellm is a Windows Excel add-in that injects a =PROMPT() function into your spreadsheets. You write a prompt as a string, point it at a cell range, and the formula returns the LLM’s response—then you drag it down to run the same prompt across thousands of rows. It supports both hosted providers (OpenAI, Anthropic, Azure, etc.) and local models via Ollama or vLLM.

The interesting bit Instead of building yet another AI dashboard, Cellm treats an LLM as just another Excel function like =SUM() or =VLOOKUP(). The cleverness is in the mundanity: it meets non-developers exactly where they already work, turning a spreadsheet into a batch-processing engine for classification, translation, and extraction without a single line of code.

Key highlights

• Runs prompts against cell ranges with standard Excel drag-to-fill mechanics
• Supports both cloud LLMs and fully local models (Ollama, vLLM, Llamafiles)
• Can act as a web scraper via MCP servers for competitive monitoring
• Free tier uses your own API keys or local models; paid tiers add managed infrastructure
• Telemetry is anonymous and limited to prompt text and options—cell contents stay local

Caveats

• Windows-only, and requires the desktop Excel app (2010+), not the web version
• LLMs hallucinate; the README explicitly warns that models may misunderstand or miscategorize data
• Telemetry collects your prompt strings by default, though it can be disabled in a config file

Verdict Business analysts, researchers, and operations teams who live in Excel should try this before asking engineering for another ETL script. If you’re on macOS, use Google Sheets, or need deterministic data pipelines, this is not your tool.