Hi SJ,
VLookUp has a 4th thingy, which if omitted, (as in your case) defaults
to TRUE. This means that if the VLookUp doesn't find the exact thing
it's looking for, it says, "what the hell" and just chooses the
closest thing it can find. This may be causing your problems. In each
of your VLookup's, you need to add FALSE as the fourth thingy.

ie.
=IF(ISERROR(VLOOKUP($B4,'P:\WIPSUM\[WIPSUM8.xls]WIPSUM8'!$B$2:$AJ
$2000,21,FALSE))*,"0",VLOOKUP($B4,'P:\WIPSUM\[WIPSUM8.xls]WIPSUM8'!$B
$2:$AJ$2000,21,FALSE))

=IF(ISERROR(VLOOKUP($B4,'P:\WIPSUM\[WIPSUM8.xls]WIPSUM8'!$B$2:$AJ
$2000,8,FALSE)),*"",VLOOKUP($B4,'P:\WIPSUM\[WIPSUM8.xls]WIPSUM8'!$B
$2:$AJ$2000,8,FALSE))

Regards - Dave.