I just wanted the highlight the fact that our friends at Microsoft have made it pretty simple to get set up to write xlls for free. I’m watching my language here as writing xlls is not simple and the documentation is not all that it could be. But getting hold of the tools to do it has never been easier.
Anyway you need Visual C++ express from here.
And the Excel xll SDK from here.
There are a few gotchas and you need to roll back some of the newer security features in VS2008. As I recall leaving DEP in default crashed Excel.
Also you need to get all the SDK files into the right places on your machine, I have a paper on this from a training course I delivered a while ago, I’ll dig it out and put it on the Codematic site (currently here) next time I’m on that machine.
Getting the files in the right place will be no problem to us Excel folks – we’re used to the misery created by externally linked workbooks, that only work when you put them in the right directory.