cross domains - tell parent frame to close an iframe

Question

I have a script that will be loaded on a bunch of sites I don't control.

My script needs to open up an iframe. The script and the iframe will be hosted on the same domain (which I control), but the parent pages won't be under my control.

When the work in the iframe is done, I need to somehow tell my script in the parent page taht the iframe can be removed.

Any ideas on how to make this work in IE 6/7 and FF 2/3.0?

Thanks!