window.opener: IE vs. Mozilla

Hi,
I have a popup date picker. As soosn as the window pops up, 'next' and
'previous' months can be browsed using 2 links.
When the user clicks on a single link next for example, the calendar is
recreated in the popup window. Now the problem is that window.opener changes
in
Mozilla from the original parent to the previous popup (from which we
clicked on next), but IE holds the original parent window although we
recreated the popup using next. I want mozilla to function like IE or
something to solve it.
Any help is greately appriciated.