Using two Smart search filters together

I have built two smart search filter drop-downs. The first drop-down returns pages based on a chosen category to my smart results web part. I would like the second drop down to filter on the results of the first drop-down, i.e. page types,so if the first filter returned all pages from category 1, the second filter would only filter on the first filters result. I have heard mention of session variables, or component events. looking for the quickest and best solution, possibly with examples.