Is there a way to "refine" the search parameters?

For example, suppose that I search Providers for "Latina, under 30, in the 310 a/c".  I press Search and view the results.  Now I want to refine my search to add "not transexual", but I can't.  When I return to the search engine, all the parameters are cleared and I have to re-input everything.

Am I doing something wrong?