All,
we have published a Student Accounting Cookbook focused on Fee Calculation and including some FAQ's in the BPX HER Knowledge Center.
http://www.sdn.sap.com/irj/scn/index?rid=/library/uuid/3077e127-f88e-2c10-a88e-f3f80f998b60&overridelayout=true
Hope it provides some useful information on this topic.
Tina