Dynamic Drill down menus

Hello, I have created a db that holds specific information ie a business name. I am running into a problem on a form when you choose the business name another list is suppossed to populate the address or addresses, if multiple occur, and you can select the address. I am not able to sucessfully pull off this dynamic drill down list in my form because I do not know how to check data from a form field that hasnt been posted through $POST VARS array. My question is, is their a way to do this in PHP? Do I have to learn javascript in order to accomplish this task or will I have to have a submit button for each form element? Thanks in advance, Daniel