Add this to the page to see what session variables are set:
<?php var_dump($_SESSION); ?>
This is for debugging purposes, but it will allow you to see the session variables and values that are stored for admin and non-admin.
To get a new rule for your page access, go to Modify->Security Assist->Access Rules Manager...
From this interface you can create a new rule "Administrator" and allow admin access if your session variable has the value it needs to have. (maybe 'y' or 1, not really sure but you'll be able to see in the dump code referenced above)