[Kirk Y]

You could change the plugin's data (Through the Plugin Manager in the AdminCP) from this:

if (!($vbulletin->GPC['logintype'] === 'cplogin' OR $vbulletin->GPC['logintype'] === 'modcplogin'))
{
   $fields = $vbulletin->db->query_first("SELECT * FROM userfield WHERE userid =".$vbulletin->userinfo['userid']);

   if ($fields['field5']){
   $vbulletin->url = "forumdisplay.php?f=".$fields['field5']; }
}

To this:

if (!($vbulletin->GPC['logintype'] === 'cplogin' OR $vbulletin->GPC['logintype'] === 'modcplogin'))
{
   $vbulletin->url = "page.php";
}

Obviously, change page.php to suit your needs.