I have a database of students, instructors, and classes. I set up a form for teachers to give regular feedback on student progress

I am able to set up a form with drop-down lists where the instructor can select themself, their course, and their student.

HERE IS MY PROBLEM:
I need to have each subsequent drop-down list filtered so that it only shows data relavent to the previous drop-down selection.

So... when the teacher picks themself out of a list, they then would only see classes they teach. When the select a class... they only see students in that class in the drop-down list.

I know how to do this manually with filters, but can't figure out how to have it occur automatically in the form. Seems simple... but I'm lost.

I see a similar request that came in just ahead of me called "Combo Box." It looks as though that answers my question.