BCGControlBar Pro for MFC
void CBCGPPlannerManagerCtrl::SetCalendar ( CBCGPCalendar pWndCalendar,
BOOL  bDropOnDaysOutsideMonths = FALSE 

Sets related Calendar control

Use this method to set related Calendar control. When the Planner has a related Calendar control, it sends and receives notifications from it about date changes. You'll be able to drag & drop appointments from the Planner Control to the Calendar, or use the Calendar to select current visible date on the Planner.

pWndCalendarA pointer to calendar control.
bDropOnDaysOutsideMonthsSpecifies whether appointment can be dropped to the day located in non-displayed month(s).