How to re-acquire same target in script

[Magus]

I'm trying to implement hit-and-run technique for a green-circle creature. So the player directs it to attack the target, it does so for one round, then falls back and returns.

I don't see how to retain original target in the second part. It seems that LastTargetedBy was meant for that purpose, but it doesn't work. Any ways to emulate it?