Can background color of frame change on userform by combobox selection on userfor

I have 4 frames on a userform, each containing the option buttons for grading a student, 1 student per frame.

what i'd really like to happen is that when a teacher selects his/her class from the combobox on the userform, the frames for the students in that class change to red...

it would be really sweeeet, if then, when the teacher clicks a button in the red frame, the frame turns to green... (at the moment, it seems easiest to have ALL students have a frame on the userform... the color change would signal the teacher where to go, and the subsequent change from red to green would remind him/her that a choice was made)

i'm attaching the workbook. i haven't attempted any code yet (actually i tried a few things but nothing worked). i have populated the comboboxes though...

any help would be so much appreciated !
this site rules !!!

-rob