trigger help!!!!!

how do you make it so when unit A enters a region all of the unit B's get removed and changed to unit A's, but only the player units that had B's in that region. Like they do in the tag games.

Stop posting multiple threads for help. Make a big thread with all your questions in them.

Event - A unit enters region 0001
Action - Pick all units within (region 0001) and do replace (picked unit) with footman.