Dynamic Drp down in search form question

Hi guys,

I have a situation I can't seem to work around:

- I have a table of 4900 employers or businesses.
- What I need to be able to do is have a search form with three elements
- Text box for entering name of employer, menu for province/state, menu for city and of course a bitton.

What I need it to do is when a province is selected from the province menu I need only the cities from that province shown.

Now the menus are populated from the table itself. For example I have the province menu items pulled directly from the database grouped by the province field, and the city menu pulled from the same table grouped by city name.

I can't seem to get it in my head on how to do this or even if its possible?

Brad