jQuery / PHP Product Filter - add functionality -- 2

I need someone to add functionality to the project filter I've been working on. It is a simple filter with 3 dropdown menus and a reset button. Right now, there is only a single level filtering as I will explain below. You can see it here: [login to view URL] The dropdown menus each select a custom post type category and they work individually, but I need them to work together. Right now if I select a category from one dropdown menu and then another from the second dropdown menu, all the results get replaced completely with only the second category. I need it to work together, so that if I select something from all 3 menus, it narrows the results down. And of course, when you come to the default selection in each dropdown menu, it will give you all results from that particular condition (application, product, region) I hope I explained it well enough, if not, then feel free to ask me. I think that it shouldn't be too difficult to do for someone who knows jQuery, but my javascript knowledge is very limited and I don't want to waste any more time.