Has anyone else had trouble determining if a modified occurence of a recurring appointment has been 'deleted' or just modifed by the user?

I have a recurring appointment.  If i open an occurrence of that appointment, and click the red X to delete the occurrence, I cannot find a way on the serverside to determine that the user clicked the delete button.  AddVariance() gets called, but how do you tell if the user just updated some of the values, or if they deleted the occurrence?