Dynamic Drop Down

Here's an easy one. I use MIVA Merchant software, and its search page sucks. I need to customize my search this way: Dropdown A, lets say: Brand Upon selection, Dropdown B shows proper models for Brand. Then the submit button simply sends the search query string of A + B to the search engine of my site. I need this to be modifiable easily, as I expect these 2 dropdowns to have close to a 1000 options combined. I am not a coder, but knowledgeable of javascript (syntax, variables, etc.) The current search page is [login to view URL] Try 'tarjeta' and 'verde' or 'azul' in your search box for the mean time. ## Deliverables 1) Complete and fully-functional javascript as well as complete source code of all work done. 2) Complete list of variables and their use. 3) Complete ownership and distribution copyrights to all work purchased. ## Platform simple javascript. compatible with anything!