[development] Question about Forms API?

Hi! I have a question about the forms api -- if this is not the best place to ask it, please let me know where I should. I want to be able to add an element to a form which is _not_ in the 'edit[]' space. Specifically, I need to be able to set the 'q' item so that it will not be lost across a GET form submission if the site is not using clean urls. Any suggestions of where to look for how to do this would be greatly appreciated. Thanks, Ricky