dazed and confused - membership

I want Logged in users to have access to different pages depending on the option checked in their User Account - in this case a Basic Member will have access to only a Basic Member page (memberbasic.php) and a Preferred Member will have access to only a Preferred Member (whiteoak.php) page.

I added this code to both the basic and preferred member pages:

<?php require_once "cmsb/lib/viewer_functions.php"; ?>
<?php if (!$CURRENT_USER) { websiteLogin_redirectToLogin(); } ?>

But I can't figure out how to restrict Basic Members from the Preferred Members page. If a basic user tries to access the preferred page I'd like to redirect him to the basic page.

Thanks.