Need to pass a value from an IFrame to its parent to its parent

[PKalos]

I'm working with the FCK editor and have replaced the File Server which
is accessed from the image button with my own.

When you press 'Browse Server' a popup window opens which contains an
iframe with thumbnails.

So we have 3 windows

1 ) the popup from FCKeditor (img_popup)
2 ) the popup from img_popup (asset_cntrl)
3 ) the iframe from asset_cntrl (assets)


What I'm trying to do is when you click on a thumbnail (in assets) it
updates a text field in a form in the parent window (asset_cntrl) and
then when you click submit it sends it back to the form in the
FCKeditor (img_popup).

I spent yestarday and this morning googling to find the answer and came
up with nothing. I cannot get the value passed to the parent from the
iframe. I'm sure that once I get this working I would just reproduce
for the next step.

regards