QuickForm Rules

I wonder if anyone knows of a _clean_ approach for a custom QF-rule which decides if a value is valid based on more than the current element's value it is assigned to. AFAIK $this->container->container will do the trick here, because a (subclassed) HTML_QuickForm_Rule object doest have a clue (no reference) which controller instance is using it, or may i be (hopefully) wrong? Usage example: -------------- A global page-rule which checks if the values in element a, b, c and d are already present in this combination in a database. It's basically like the login/handle-rule i explained some days ago to someone on the list, but a little more complex. A grouprule would not of interrest for me, because of the generative structure of Page objects and its effects on the renderer. Yours :Matthias