TSM 5.1.8.0 on AIX

Is there a way to easily determine the size of a backupset?

I track tape occupancy weekly to chart growth of our TSM system.  Each
Excel spreadsheet has an embedded "select from occupancy..." query.  That
allows me to determine how much data I have and where it is in about 5
minutes.

But data in a backupset does not show up under any "occupancy" measure
that I'm aware of.  As I shift more archives to backupsets, I'd like some
way to show that the reduction in archive space isn't real - that data is
just changing form to backupsets.  That way I could count the backupset
data along with all the other data I'm tracking.

TIA

Tab Trepagnier
TSM Administrator
Laitram, L.L.C.