Switch Case code to redirect from a link based on session variable

I'm writing a web app (php/mysql) for a college with 29 departments. I have a login page which checks username and password against the DB and if it finds the user also pulls down an access_level variable:

$loginStrGroup = mysql_result($LoginRS,0,'access_level');

//declare two session variables and assign them
$GLOBALS['MM_Username'] = $loginUsername;
$GLOBALS['MM_UserGroup'] = $loginStrGroup;

//register the session variables
session_register("MM_Username");
session_register("MM_UserGroup");

Then, based upon the access_level stored in $loginStrGroup, I redirect the logged in user to one of five pages by means of a switch case expression:

switch ($loginStrGroup) {
case 1:
header("Location: switchboard01.php");
break;
case 2:
header("Location: switchboard02.php");
break;
case 3:
header("Location: switchboard03.php");
break;
case 4:
header("Location: switchboard04.php");
break;
case 5:
header("Location: switchboard05.php");
}

All that works perfectly. Here's my problem -- some pages in the app need to be shared by users with different access levels. On one such page I have a link back to the switchboard, but it's a hard-coded link and returns all users back to just one switchboard.

How can I reference the session variable $loginStrGroup in such a way that any user who clicks the link will be sent back to his/her proper switchboard? I've tried a few variations in code but can't get it to work.

Thanks.

Jerry