Nested select options from database.

Hi everyone, Is it possible, using just PHP, to pull a select menu from a DB, then when the person makes a selection have it populate a second drop down select menu, and again for a third one? Would javascript need to be involved here to keep it all on the same page? I'm in pretty desperate need of some code that can do this to select categories for products to go into, and I'm not sure how to make it work. There are way too many categories to have top level, second and third in the same drop down anymore - we only want people to be able to add the products to the third level. Krista