Then, i think you have this situation: a main page and a popup with 2 frames, right?
Let's suppose that the structure of your popup is something like this:
<frameset rows="50%, 50%" border="0">
And let's suppose too that the structure of your main page is something like this:
<textarea id="mainText" name="mainText" rows="6" cols="60"></textarea>
If you want to pass text content from the "page2.html" in the popup to the main page, you can do it as the follow:
//code in page2.html
parent.frames.opener.document.getElementById("mainText").value = "SOME TEXT";
I've simulated here and it worked.
I hope this can help you. And if you need some help, post again!