Custom validation messege

Hi

I have a column in my database for various accesslevels to my site. I have set this up with 4 levels (admin = 4, student = 3, registered = 2 and visitor = 1). When a user register he is assigned accesslevel 2 in database
On my loginpage built in SA I have set up a rule allowing accesslevel 3-4 to login successfully and also restricted accesslevel 2 since I don't want registered users to access my site until they are approved. When a user who has just signed up through the registration page is transfered back to the login page and tries to login with his registered email and password he won't be able to login since the rule is set to restrict accesslevel 2 users. I solved this by redirecting unsuccessful logins to another page where Ive just set up 2 server behaviours, clear all sessions and server redirect back to the login page. All this works good.
My question is how I can show a messege to a registered user when he's transfered back to the login page after a unsuccessful login attempt, displaying that he can't login to site until his registration has been approved?

Thanks in advance!

/Martin J.