Spread32 is fully compatible with Microsoft Excel! It is essentially a mini-Excel with all of the basic features that you would expect in a competent spreadsheet program. Run macros, draw objects, generate charts, calculate functions and formulas, its all here. And it reads and writes xls, csv, text, and pxl formats.
Spread32 is a tiny spreadsheet program that supports 256 columns x 65536 rows x 255 sheets, formulas with over 300 functions, sorting with multiple keys, freeze panes etc. It may not have all the bells and whistles of its beefier cousins, but it is an excellent choice if you just want to fire up something instantly for some quick-and-dirty calculations.