XML - Search and Display

**FIRST PART:**I am creating an application where users can select certain types of products by selecting up to three items from three drop down lists. Once they select the items I want it to do a search. Between the lists I want to generate a number (or rank) and then display all products within an XML file that are within a certain range of that rank.

I don’t need any ActionScript, just a push in the right direction. What method would be best to do this?

SECOND PART: Secondly, I want to give users the ability to pull a certain category for a product and display all products within that category.

Again, just a push in the right direction. What method would be best to do this?

In total there would be over 100 products, each with its own rank within a category and/or search.

Any help is much appreciated.