Enrolment

Hello Can anyone help me with my issue, bit of a newbie here. We will have two courses in our system. The first course will be for students that get it as a benefit of other products we offer so this will be free to them and we'll be adding these users via the upload tool. We will also have a different course with will be paid-for by other users on a per-user basis via PayPal, which auto-enrolls these students following successful payment. I have everything working except I can't hide the paid for course from non-paying students without it also becoming unavailable to joe-public as well. How can I stop non-paying students from seeing the paid-for course which is only available to joe public? any ideas? Thanks matt