Filtering a list/grid to exclude previously selected items

Hi All,
I’m trying to figure out how to filter a list so that previous selections made by the user are not included. For example, I have a list of courses and the user selects a course. The next time the user searches for courses, I want to exclude the course already selected.

I tried filtering by Logged-In User in the source, but it only offers the option to select courses “with” user = logged-in user. If I had the option to select “not equal to” or “not containing”, that would work perfectly but that’s not an option.

Looking for some other ideas on how to best accomplish this.