How can I add the control to the configuration screen of a calendar event? overlapping of events or if the same user "assigned to" already has an event in calendar (even partial) between "Start date and time" and "End date and time" of the new one event by clicking the "Save" button a warning popup must appear with the message "It is already present a calendar event at this juncture, we want to proceed?"
The selection YES will create the calendar event, the NO choice will return to edit mode on the event.