how to create temporary user ?

dear all...im using freeradius-1.1.6 and mysql database engine i have a problem.. i want to create a user that only can login in specific dates.. for example user A can only login today (max 12.00pm this night) user B can only login today and tomorrow (max 12.00pm tomorrow night) user C can only login between 2007-05-20 to 2007-05-25 what attribute i should use ? thanks