Url of a fully loaded page

[paratge]

Hi,

How can i know if a page from annother domain is completely loaded in
an iframe, cause i must read it's url which is not the one i sent to a
cgi script. It returns an encoded url with Hmac key i must read to
create a temporary user account named as the key.

I tried many things but all what i got is the address i sent first.

Thanks in advance for your help.