not sure exactly what you want..
so you have group "A" units that spawn, and after X amount of seconds you want them to attack group "B" units?
havent used world edit in awhile as in a year or 2..
so wouldnt action be create group "A" units @ region XXX, wait X seconds, and then attack group "B" units
condition would have to have attack units equal to group "B"
if not equal, stay @ region XXX
i dont know

i have little experience and just rambling off top of my head