SPARTA allows you to handle seperate members areas for trial members and full members and even allows you to use the same members area but figure out if a certain member can access a certain page. You can do so if you use NATS authentication. A trial member will then have the apache note sparta_trial defined and thus you know that this member should only get access to certain files.

Even when you do not use NATS there are ways to handle trial members areas via the mySQL authentication system.