casters with art, how to make them unselectable

hey, i have a few dummy units to cast spells and some of them have a visible model, how do i make them unselctable for the player else than adding locust skill? i need this because i need to be able to select that unit with "GetUnitsInRectOfPlayer(gg_rct_X, Player(PLAYER_NEUTRAL_AGGRESSIVE))" and with the locust skill thats not posible (i already tryed) and alowing the player to select a caster would be wrong.

Thanks

Add them to a global group and then give them locust, then when you need to group them up, just add the global group to the group you're enumerating in.