Beyond is right however I would strongly recommend you move to focus for leader

this way
Code:
/cast [target=focus,nodead, help][target=player, mod:shift][] Regrowth
would be used to cast regrowth on your focus (the lock) unless he is dead (or your focus is an enemy somehow) if you press shift while casting that spell it will cast on the drood and if you have no focus and shift is not held down it will behave as if no conditions were specified and cast on your target if it can heal it or the druid if it can't