Thanks for your reply Richard. I appreciate what I'm asking is not simple.
I think that I have actually found a solution myself. Currently teachers have permissions to access the CSV upload where they can upload students and use the CSV to enroll them also. Simply I wanted to stop teachers enrolling students on to courses the teacher themselves were not already enrolled in.
I may have found a solution in PHP and editing the userupload/index.php by comparing all courses and my enrolled courses but I am still testing it.