Is this possible (Excel 2002)

We have a workbook in a shared folder which many need to have access to
update the info in it. Problem is there are now 3 versions as obviously
someone has created a copy and entered info in that one and not the original
- there are 15 sheets in each one and now I have the horrible job of trying
to work out which sheets in each are most up to date and merge them back into
one - GRRR!