cancel combobox update

[Patrick McGuire]

I have an unbound ComboBox whose RowSource is a SQL
query. I'm PRETTY sure that the values in the pulldown
list are all valid, but I want to trap any errors that
might arise from invalid selections. Unfortunately,
canceling the update using the BeforeUpdate event doesn't
seem to work (i.e. the OldValue doesn't actually equal
the last valid selection). I suspect that this is
because the ComboBox is unbound. Any suggestions?

Thanks,

Pat