first thing, you need to create a list of all west units
2 methods
1) Place a repeating, activated by anybody trigger encompassing the entire map
and from this trigger retuirn a list of all west units
See following thread <<
http://www.ofpec.com/forum/index.php?topic=27814.0 >>
or
2) if there are only a few units, create an array of all the west units
eg
_Warray = [W1,W2,W3,W4]
and then use following condition
{if ((count _x in _veh) ==(count _x))then{do whatewver you want here}}foreach _wunits
code untested should work