Enrolment

We are using Moodle version 2.7, we are using MySQL for the enrollments.  Our system is integrated with genius, so our user enrollments are managed through this system.  Once a user is enrolled and they log in to Moodle it triggers the enrollment and they are in the course in Moodle.  The problem we are having is that the users are not coming out of Moodle when they are finished with the course.  It is requiring a login from the student as well in order to trigger the un-enrollment in the course.  Many of our users are still showing up in the gradebooks and look as if they are still in the course, when they really shouldn't be.  Sometimes our students are only taking one course, so they might not login again.  I know there is an expiration that you can set on Manual Enrollments, does anyone know of this for external enrollments.  Or any other solution to this issue?  Just some way that would trigger that un enrollment besides having to have the student login?
Any help would be appreciated!!  - Angel