I'm trying to figure out who is using the iframe snippet I posted on my site. Is there a way to get the url of the page that is displaying the iframe?

This doesn't work but something like this:

www.mysite.com/my_content.html
HTML Code:
document.write( "this page is being displayed at" + document.getElementById("iframe_id").contentWindow.location.href );

www.someothersite.com
HTML Code:
<iframe id="iframe_id" scr="http://www.mysite.com/my_content.html"></iframe>