simple but important question... deleting units for nonexistant players...

I can't figure out a way to delete all the units placed on the map
for any players not in the game... for example if only 2 players
join a 4 player map.. i want the units for players 3 and 4 to be
killed upon initialization.... any ideas?

Only way I know to do that is to create the units with a script which only runs if the player exists.

use the IF/THEN/ELSE and player slot comparisons

if (player 1 slot status) is EQUAL to IS PLAYING then do XXXX else XXXX

Hm... yeah, just noticed Blizzard's RPG is using that trigger as well.
Say, is it possible to give multiple units (like all units owned by a player or all units in a region) to another player or delete them and that with only one action? The world editor seems not to be capable of that - takes half a dozen of actions for even the most simple things.