> I want to show the actual database filesize in a statusbar,

Curious, cannot imagine why a normal user should care about
the database file size. Whatever...

IB_Connection.Characteristics

dbAllocation
dbPage_Size

attributes are the ones you want, multiply these to get the
total bytes (but be careful of overflowing a cardinal, you
could need a 64bit value if your database may be large).

--
Geoff Worboys
Telesis Computing