You'll need to modify your data model, but first a question:
Could a given document be associated with more than one course? Right now, you data model does not support that possibility.
Putting that detail aside for the moment, You can add a field to the professors table: SelectedCourseID
Clicking a record in portal to Prof_Course could run this script:
Set field [ Pro_PRO::SelectedCourseID ; Prof_Course::CourseID ]
If you then set up a relationship linking SelectedCourseID to the CourseID field in an occurrence of Documents, you can set up a portal to that occurrence of Documents to use for displaying the documents for a selected course.
Thanks for the quick response.
To answer your question, no, a document will always be associated with only one course.
Just a quick question: will your suggestion allow me to still display the details of the course in the global fields I have on the layout?
My suggestion does not use nor require global fields.
Thanks again. It works just fine.