Class Enrollment App - Custom Reporting

[Anya]

We are using the Class Enrollment Free app. We have Contacts who are of Contact Type "RBC". While the app comes with standard reports for listing which students have enrolled or have completed a particular course, we would like to find a way to run a report that shows which RBC contacts have NOT taken a particular course. So, system who retrieve all RBC Contact and determine if each has or has not completed a certain required course or courses.

Anyone?  THANK you in advance!