Possible to find out if iFrame content has changed (V7 BrowserFrame) ?

My vaadin 7 portlet is running on one server, a system providing some forms is running on another machine. These forms shall be displayed within the vaadin application/portlet.
At the moment we are using a vaadin BrowserFrame, which works well. The form is filled out and submitted, after that a confirmation page is displayed.
We would like to remove the BrowserFrame component from layout when the form has been submitted. Manually via button is of course no problem.
But: we would like to have an automatic reaction. For example: when the confirmation page loads, some listener/method is called…
would that be possible?

One idea is to have a servlet attached to a url-pattern that is unique to the confirmation page. The servlet would serve the page back, but could also notify your application. At that point you would remove the browserframe component and initiate a server push so that the gui would be updated.

I do something similar where I need my gui to update based on browserframe activity. When the user logs in, I pass this information to the servlet, and it notifies the component when appropriate. This is my notification routine in my servlet:

private void notifyUser(String userName, String url){
        UrlFilenameWatcher interestedParty = watcherMap.get(userName);
        if (interestedParty != null){
            interestedParty.notify(url);
        }else{
            logger.error("BrowserHistoryInterceptor: no url watcher found for user "+userName);
        }
    }

My watcherMap holds the Vaadin component implementing my UrlFilenameWatcher interface.