From prompt to Excel custom function in 30 seconds

xllify is a packaging tool and runtime that allows functions written in Luau and Python to be used as high-performance custom functions in your Microsoft Excel workbooks. In a bizarre collision of 1990s style development (the Excel C SDK) and 2025 era AI, I’ve been experimenting with having a Claude agent write Excel custom functions for xllify! As Excel itself is now fat and 40 years old, it could be donning ill-fitting running gear and developing an irrational interest in coffee beans....

November 18, 2025 · Alex Reid

xllify is out

Back in August, I introduced xllify. This was a project I started when in-between contracts. I’ve since distilled my definition of xllify to: xllify is a packaging tool and runtime that allows functions written in Luau and Python to be used as high-performance custom functions in your Microsoft Excel workbooks. Go have a look! Things have evolved. As with all projects, I try to ruthlessly simplify and make things faster....

November 18, 2025 · Alex Reid

Fast and easy Excel custom functions with xllify and Lua

Excel is the original rapid application development tool. Developers can do unholy things to get the job done with no code, or perhaps with just a smattering of VBA. Long term, these solutions can end up brittle and hard to extend. Over the years there have been many approaches for extending Excel beyond formula soup and VBA. There is the excellent Excel-DNA, PyXLL, Microsoft’s own Office.js and Python support, among others....

August 27, 2025 · Alex Reid

Taming real-time data in Excel with rtd.pub

rtd.pub is a platform for easily connecting any real-time data source to Microsoft Excel. You can write code in Go and Python, or simply configure pre-built open source connectors. This is a design and approach I’ve been mulling over for the past couple of months. I have now implemented it. This, and of course spreadsheets in general, are somewhat boring. However, they’re the original low code/RAD tool: in terms of bang for buck and the control they put into the hands of domain experts, nothing comes close....

July 3, 2025 · Alex Reid