Workbooks(WBSource).Sheets(SourceSheet1).Copy Before:=Workbooks(WBTarget).Sheets(Var1)
you need to break this line down to find out which variable is causing the error

i am assuming this is in excel 07?
if the name of your workbooks and sheets are all correct, from the posts in this forum this may have been a common problem with early office 07, fixed with some service pack or other

there are work arounds to avoid the error, but possibly better to get any service packs

your code further down works with sheets, but does not specify which workbook