Sure, no problem was just an idea
For your script, if you don't want to use a script but incorporate Kendo's idea you can do it in triggers.
You'd need 5 triggers
Create the groups as Kendo said, and give them 2 waypoints. The first a move to a bit infront of their start and another as an attack (or search and destroy or whatever) to the ambush site.
Then create 3 triggers, each of which is a switch type and put these into the conditions:
RAN > 1
RAN > 2
RAN > 3
Then syhnchronise each one to the unit type (eg. ran1 to the troops, ran2 to bmp and ran3 to helos, or whatever you want)
You will need a trigger which activates immediately (maybe put it in the init file) which has the following in the on activation:
RAN = 4
It doesn't matter how it trggers, it could be anyone present on the whole island, or it could be no-one present in a tiny area, either way make sure it firesa immediately.
You will need another trigger which will detect when the ambush will happen.
Place the trigger in the ambush siter and set the conditions (these could be if you get seen or if you are jsut there, or maybe off another variable, but that's unlikely)
Then have in the on activation:
RAN = random 3
That should give you the same effect as the script, you can see why the scrips are so effective, lol.
Anyway, good luck