I've been looking into getting the extended forms javascripts that are out there to work with this. So far I've not had much luck getting them to work. What I'm talking about is this:
http://www.quirksmode.org/dom/domform.html
Has anyone given this a shot yet or have a better idea of what should be edited? So far, I haven't even tried to see if they submit, as I can't get the extra fields to generate just yet.