Enrolment

Any advice on how to go about doing the following?

We would like teachers to be able to leave cover (substitute) lesson plans (ie. for when they are absent) within their courses. Problem is: unless the covering teacher is enrolled in that course, how do they see the cover plans?

At present we have all teachers force enrolled by site admin as non-editing teachers in every course, but you can imagine how inefficient that is. It also appears to cause problems with subscriptions to forums, etc, as everyone then gets lots of unnecessary messages.

We could allow teachers to simply enrol themselves as and when they need to, but if a course has used an enrolment key then they can't do this.

Any suggestions would be much appreciated

David