Trouble with logout hash for vB 3.8

[Mobo]

Hey guys, I'm having some issues with the logout hash for a customized home page - I'm trying to feed the logout to the vb forum logout page through the following code:

$logged_user = ($HTTP_COOKIE_VARS["bbuserid"]);
$logged_pass = ($HTTP_COOKIE_VARS["bbpassword"]);

$license = "<mylicense>";
$logouthash = md5($logged_user . $logged_pass . $license);

<a href="../forums/login.php?do=logout&logouthash=$logouthash">Logout</a>

I suspect the problem lies with the $logged_pass, since it has already been encrypted. Anyone know how to get around this, or how I can better implement this?