should I continue using Excel2000 DLL or xl2003?

I have a excel addin project ( class library ) which references xl 2000. The application works fine in Excel 2003 also. I pass the Excel instance to the class library and the project reference to xl2000.dll (Interop.Exce). So at compile time, the code referes to xl2000 library and at run time, I pass the Excel.application to my class library.

I am moving to Excel 2003 and when I set reference to Microsoft Excel 11.0 Object Library, ie. xl 2003, I am seing lot of compile errors and I think several object methods have a different signature than xl 2000.

My question is, do I need to set the reference to the xl2003 dll?. or can I referes to xl2000 and at run time, pass xl2003 reference to my dll ?.

Please let me know. thanks

[752 byte] By [krishnakumar] at [2008-1-5]