Splitting out to .csv files is a good idea, but it does have some issues.  First, a .csv can only save out one sheet at a time; manually saving out 200+ sheets would be mind-numbingly painful (hopefully VB would/should be able to automate this task).  Second, the resulting 200+ files are coming close to the maximum number of open file handles a 32 bit Perl can handle (depending on how many derivative files are created it could be uncomfortably close).  The number of file handles becomes an issue because it sounds like the OP is doing some massive cross-referencing between sheets (meaning most, if not all, of the .csv files would need to be open).  Seconding a previous post, this file should have been entered into a database long ago...