Troop Respawn after embark on helo

[yeldraw1]

I want to have say 6 troops that embark on helo, and once they are loaded, 6 more troops appear so they can be picked up.  I want this to be continuous, I dont want to have to make a lot of copied troops.  I can respawn them if them are dead but not if they are loaded in helo. not sure what Im asking can be done.