I am trying to create a parade tracker. We want to use a series of polygon blocks and 2 gps devices. The polygon blocks are the route of the parade, and the devices will be on the front float and the rear float. We want the 1st device trigger/change the status field from Null -> LEAD. Then as the 1st leaves that block, change the status -> MIDDLE. Then as the 2nd device comes along, it changes the blocks From Middle to TAIL. And finally when the tail leaves that block, change back to null.
The end result we are hoping for is a snake effect.