using postmessage to refresh iframe's parent document

Question

I have a greasemonkey script that opens an iframe containing a form from a different sub-domain as the parent page.

I would like to refresh the parent page when the iframe refreshes after the form submission

I am at the point where I can execute a function when the iframe refreshes, but I cannot get that function to affect the parent document.

I understand this is due to browser security models, and I have been reading up on using postMessage to communicate between the two windows, but I cannot seem to figure out how to send a reload call to the parent with it.

Any advice on how to do that would be very helpful

thanks