opener references the parent, so in your javascript you should be able to use that.
for example, if i wanted to assign a text field in the opener window from a text field in the popup, i would assign those fields ids and do something like this in the popup:
Code:
opener.getElementById('my_text_field').value = 'blah';
might need to make it opener.document.getElementById .. i haven't tested it.
report back what you find.