OS Commerce; Currency to Points

I've setup a shop using OS Commerce. Upon purchase of goods within the shop I'd like the customers "points" balance to be debited. So; 1) Create an extra field for the customers called "Points," inputted manually by an administrator. 2) When an item is purchased using "Points" the field is debited accordingly. 3) The customer should be able to view their points balance in "My account." That’s it. Will answer any messages through PM.