I am working on a C# application that generates Excel spreadsheets using
Excel APIs. My scope includes support of Excel 2000 and greater (Excel 2002,
Excel 2003) etc. Unfortunately, the required parameters for each API have
changed with the different versions of Excel. For example, my program works
fine with Excel 2000, but does not work with Excel 2002 or Excel 2003 because
the APIs have changed.

What is the best strategy to use so I can write the application as simple as
possible, but at the same time support the various versions of Excel that are
available including yet to be released versions?

I know there are third party tools available, however I do not want to
increase the license cost of the product and require third party software
licenses when the user of my application already has Excel.