Frames address BIG problem

[cmadeira]

I'll be long, because I know this is going to be tough...

Suppose I have a page at one site (

http://www.site1.com)

with frames imported from a second site (

http://www.site2.com).

What I want to know is how to get javascript, by means of location or url or host or something, to give me, inside one of the frames, the address where the parent frame is.

Explaining again: I want to investigate in one frame if the frame is being called from

http://www.site1.com

or elsewhere.

I just checked about everything in last four hours and got nowhere.

Thanks.