Tracking an iframe and setting it's parent page as the Referrer URL (no replies)

My users can embed an iframe from my site on their sites. I have Piwik working well and it tracks each time the iframe is loaded, but I really need to know which website is loading it.

Is it possible to set the Referrer to the page that loaded the iframe? I'm using the js tracking API (not the php one) and all Piwik code is inside my iframe.

I was hoping I would be able to do something like this from within the iframe:

var _paq = _paq || [];
_paq.push(["setReferrerUrl", document.referrer]);
_paq.push(["trackPageView"]);

Is there any way to do what I want?