One thing you might be able to do is pass a variable to the main frameset page via the URL that changes the page in the frameset, something like:
http://myhost/framepage.php?https=1
<?
$framesetpage = "default.php";
if ($https == 1) {
$framesetpage = "login.php";
}
?>
<frame>
<frameset page="<?= $framesetpage ?>">
</frame>
excuse the horribly incorrect html tagging, I don't remember how to make frames off the top of my head :-)