tough question

I am trying to create a button where a user can upload a photo of theirs to a server for their account. Now the uploading is not a problem. The problem is that the registration page is done in flash and then a button opens a popup window using getURL. The popup links to a PHP file that will let the user select their photo and then upload it.

Once the upload is complete and the popup window is closed, I want flash to add a preview to the registration page. I need a way to either send flash the filename (once the upload is complete) or create a function to wait for the popup window to close.

I just need the proper trigger once the upload is complete. Any suggestions would be really appreciated.