Most Excel automation starts the same way: you record a macro, you improve it, you copy it into another workbook. Over time, those macros accumulate. Some live in PERSONAL.XLSB. Others sit inside operational workbooks. A few get emailed around the company whenever someone needs them. Eventually you realise something uncomfortable: your automation has become useful enough that other people rely on it — but it has no structure, no versioning, and no clear way to distribute updates.

This is the point where many Excel developers discover the .xlam add-in format.

An Excel add-in allows you to centralise automation into a single managed file that loads into Excel at startup. The macros become globally available without being embedded inside operational workbooks. Instead of copying code between files, you maintain a single source of truth.

In this series we will take the perspective of a single developer building an automation library that can later be distributed to colleagues or deployed inside an organisation.

By the end of the series you will have:

• a structured VBA add-in project

• a version-controlled codebase

• a repeatable export workflow for Git

• a signed add-in ready for enterprise deployment

But the first step is simply creating the foundation.

Creating the Add-In Project

Start with a completely new Excel workbook. Save it somewhere dedicated to development. A simple structure like this works well:

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