HTML Frameset Header Referrer Form Email Issue

When people fill out a quote form that is inside a frameset on 2 separate locations, we have no way of knowing which agent referred them. This is the problem we need to solve. We need to capture the URL for the frameset and send it along with the form results. This shouldn't be a hard task. Frameset must stay in HTML and not be totally PHP includes as client edits and only knows HTML.