Add a billing options that allows you to create an event or item that has multiple billing points

It would be helpful if there was an options to create special billing groups for shows and exams as an example if a student enrolls in an examination there is several fees associated with this such as exam fee, admin fee, mock exam fee etc it would be helpful to be able to create a special billing item that would include all of these fees and allow us to be able to assign the appropriate billing category for our book keeping as right now we have to enter ench item separately per child per level etc. This could also be used for show fees, competition fees etc.