IndexTrader,
I think you should try Visual Basic, because it's the build in language for Excel and it's really easy to use native Excelfunctions.
wesman,
I started with my "Excel-project" about 10 months ago, now it is an own program with several thousand lines of code. It is still written in Visual Basic for Excel and it is still using Excel for in- and output, but at his point I can't call it an Excel-program any more.
Sharing the sourcecode wouldn't help you a lot, there is almost no documentation and it is also in german.