I forget how we used the point system, but I will share what I do remember. We had mandatory events such as rush, mixers, weekly dinners, alcohol awareness and sisterhood, scholarship, philanthropic, and community service events. Attendence was mandatory unless you had a class, work, illness, or an unforeseen emergency. You had to have a certain number of points in order to attend the formal. There were certain optional events for which you could receive additional points in case you missed a mandatory event. If you missed a mandatory event without an excuse, I think that you had to pay a fine. I forget the details. I just remember it wasn't very successful. It was hard for sisters with evening classes to attend some of the events. They weren't penalized, but they had to call and excuse themselves. Ultimately, we never had the heart not to let someone attend the formal.
Anyway, I hope that it works out better for you.