Advanced search: two fields for two categories problem

Hi,

I have two categories: 1) Cars, 2) Prices. In these two categories there are a few subdirectories. I want to make an advanced search that will use two fields for each category: one for “Cars” (and its subdirectories) and one for “Prices” (and its subdirectories).

I go to Theme Setup -> Search Setup. When I add a taxonomy field there’s a taxonomy that lists all categories. That means I have one search field for both categories. I want two fields for each category.

Am I missing something ?