Hi fredlef:
I don't see why not. Below is a simple example where the Subtotal function has been used outside the original table. I guess what you are really doing in such a case is practically emulating the sum function -- unless I am missing something here!
name hours
Joe 40
Joe 42
Joe 46
Cathy 50
Cathy 32
Bob 48
Bob 36
Bob 54
Joe's SUBTOTAL =SUBTOTAL(9,B2:B4) 128
Cathy's SUBTOTAL =SUBTOTAL(9,B3:B4) 82
Bob's SUBTOTAL =SUBTOTAL(9,B7:B9) 138