I want to load a movieclip into a movieclip the file is retrived from a URL variable

eg.

page.php?url=foo.swf

and have this in my web document:
<PARAM NAME=movie VALUE="index.swf?pg=<?php echo $_REQUEST["url"];?>">

and in Flash

loadMovie(pg)

But I want to have a test where I test if pg is empty or not

eg. something like:

/*
If not pg load default page
/*
if (!pg) {
//Load default page(eg. default.swf)
}
else {
//Load pg)
}

But I just can't get things to work, can anyone help

regards T