running total in sub form

[dbprgm]

Hello,
It is real easy to add a running sum control in a report.
All you do is add the textbox, enter the calculation, set
the RunningSum property to GrooupAll and it does it for
you.
Is there anyway to do this in a subform, seeing as how
that property is not available in a form.Any advise would
really help.
Thnx,
Prgm