Passing data from one frame to another

[jbeck]

I have a page called Reports.aspx with three frames. One contains header.aspx the other contains tree.html and the third looks like this

<frame name="rpttarget" id="rpttarget" frameborder="0" marginwidth="0" marginheight="0" scrolling="no" />

tree.html contains a javascript menu that loads a .pdf to rpttarget. I need to get the url from rpttarget on a button click event in header.aspx.

Is this possible??