Check whether form in iframe has been submitted

Ok heres the deal. I am trying to create my own "co-registration path" for my co-reg websites. Basically, its just a bunch of iframes displaying interactive ads within one page. What I need: I need some sort of code or certain "function" written, Im assuming it can be written in javascript, and probably only in javascript, where the page can tell whenever the iframe form has been submitted, or the url has changed within the iframe. So for an example, I have one iframe on my page, which displays a form. I need to track whenever that form in the iframe has been submitted. Im not sure if that exact thing is possible, but if you can make it tell whenever the iframe source has changed, that would work as well. I know this is possible, I just dont know much javascript. Perhaps creating an interval checking if the URL has changed every second or so would work. I really, really need this and will very much appreciate anybody doing this for me! I will definitely award a bonus if done fast! Thank you!!!!