How to set a Calendar alert for AFTER completion of an event?

I would like to set calendar alerts to happen at the scheduled completion time of my events - whatever that may be. I can't seem to figure out a way to do this. You can create alarms that go off before an event starts, at the start time, or a fixed number of minutes after start time. But is there a way to set an alarm that triggers AT OR AFTER the completion time of an event, without having to specify the exact date & time?