How to tie a dropdown list to a gridview in Sharepoint 2007

This should be a really really simple thing, but for some reason it is just eluding me.

I want a Sharepoint page which will have a drop down list that is tied to a database lookup table.

When an item is selected and they click a GO button, I want it to update a gridview that is also on the page.

I'm looking for a simple how to – while assuming I'm a sharepoint idiot. BTW, I am using the Microsoft Office Sharepoint Designer.

Thanks,

Edit:
My need is actually very simple. I want to filter the results of a query using a drop down list. This used to be called a master – detail relationship.

For example, my regular data has school name, application name, and how long the application was running. Because there could be a hundred applications per school and there are 60+ schools, I only want to show one schools information at a time.

So, I want to put a drop down list at the top of the screen which contains the list of schools. When one is selected, the gridview should be updated to reflect the new schools information.

Chris.