Swarm in action

Today, as I was frantically getting equipment ready for Farmer D's, I heard the hum of a swarm.  I looked up and yes, sure enough, they were off and going.  I follow for a few mins, but really I was already running late for a day packed with important appointments.  I have already add one or two boxes to every hive and rotated the brood boxes, but once it's in their intent to swarm it's to late to stop it..