Memory/CommittedBytes question

I have an app that allows users to select data from a database.  However, I
would like to prevent users selecting an excessive amount of data and
bringing their workstation to a standstill.

Would it be right to watch the Memory/CommittedBytes value, and stop the
data fetching operation when it exceeds the installed physical memory by x
amount?  Is there a way to retrieve the Memory/CommittedBytes value aside
from looking into the windows performance counters?

Thanks.


Ray Mond