It's bound column is the ClassEventID, which determines what class session the students will be enrolled in when the btnEnroll_click() event runs. It should also determine what shows in the other fields at the top of the form: ClassName, ClassType, SessionDate, etc. That way the user can see the important details of the session and know s/he has picked the right one. All those other fields are disabled and locked.
I don't actually want to edit any information about the class session from this form, I only want to choose a class session for enrolling students.