Filter Searches using drop down boxes

Hi all,

I am currently working on implementing a new search feature to our webstore.  Ideally here is what I want to achieve;

Have for example a couple of drop down boxes, one saying Manufacturer and another saying category.

Now lets say for instance a user selects Hewlett Packard from the Manufacturer drop down box, I want the category box to populate with all the relevant info within the HP category.

How can this be achieved dynamically? Has anybody else implemented something similar? And do we need SuiteScript to achieve this?