Custom validation issues

I am attempting to set validation criteria, so students are not able to complete a question block if they have selected an instructor which does not teach that course. Course 1 is taught by instructor A. Student has selected Course A, but has selected instructor B = error message occurs via custom validation.
The available selections are made available to students through "pass-through" fields.
I am getting/not getting the desired output using the current logic set up.
The current logic works as expected if the student only selects one course and one "correct" instructor OR one "incorrect" instructor. But if the student wanted to evaluate multiple courses and multiple instructors throughout their survey this leads to the following issue:
The current logic will allow the student to progress to the question block if any of the instructors listed within the validation logic are "displayed" and not "selected" though "selected" is the final variable.
Any thoughts/insight would be appreciated. Thanks in advance. Happy Holidays everyone!
Duffy