Combo boxes and values

[alpokorny]

I have a very small and simple database that I want to capture som
basic expense information with. I want to have a combo dropdown bo
display a list of values (expense groups) on a form that a user ca
select a list entry. Then I want an adjacent combo box to display
list of values (expense categories) that vary by the selection made o
the first combo box. what's the easiest way to do this.

Thanks for your help