Well, ever tried a periodic trigger? You can probably just keep panning it. So say if you were to have it move around once initially. You can do this afterward:

Constant Pan
That might work if that is what you are looking for. If you want it to pan around the area
once as long as a condition is running, I think it would be kind of hard. I guess you would just have to calculate the time somehow or just estimate it, and wait that long..