Packaging and reusing VBA code in Excel

So, I am using Excel 2007 .xltm templates with data connections to SQL Server to output report tables. Each file has multiple VBA functions to manage update, shutdown, formatting, user input, etc. I have 50+ .xltms with the same set of modules, so its quite cumbersome to change all of their VBAs.

Is it possible to code excel VBA to link to external VBA files? This way, when I make changes, I only change it in the main vba source file. This might be a stretch, but is it possible to write a / .NET dll module that will import the .bas file when opened?

Thanks in advance Matt