As this is thread is relativ old I think it has been already solved.
Our solution was to create a new class with the interface of IF_BSP_DLC_OBJ_TYPE_CALLBACK. In the method you could add the following lines:
IF iv_object_type EQ 'BT126_APPT'.
lv_sub_type = 'Z100'.
APPEND lv_sub_type TO result.
endif.
After the succesful generation you could add this callback to the view of
SPRO -> CRM -> UI framework -> UI framework definitation -> Define UI Object Types
add a new entry:
Object type: CUBT126HAPPT
callback class: the created above one.