BBP_EVENTS_DET_CLASS_NAME implementation

Hi ,

Any one implemented method BBP_EVENTS_DET_CLASS_NAME  of class BBP_ALERTING ? What is mean by define message class ? I have a requirement to send mail for a group of users when contract is created. For overwriting I can use BBP_EVENTS_DET_RECIPIENTS  method. But I am not getting how to implement method BBP_EVENTS_DET_CLASS_NAME  for Mail body and Subject line . Can any one help on this .Thanks In advance.