Need help with making a spell

I need to make a spell that periodically attacks nearby enemy units automatiacally.

So far, what I have done is: Modify scout so that it summons a "Storm cloud" unit. Once this unit is created, use JASS to make it follow the hero casting the spell. This unit will then attack nearby units on its own.

However, what I need to do is to PREVENT the user from ordering this created unit around. Anyone has any idea how I can do it?

Also, it would be even better if someone can just teach me how to make the unit completely unselectable and invisible even to the owner player.

If anyone has any other way of implementing the spell, please tell me as well.. Thanks!

Give the creature to an AI player who is allied with the human player.

Try giving it the aloc ability I think it's ALoc but it might be Aloc...

To prevent the player from selecting you can try:

Prevent Selecting
Events
Player - Player 1 (Red) Selects a unit
Conditions
(Unit-type of (Triggering unit)) Equal to Storm Cloud
Actions
Selection - Clear selection for Player 1 (Red)

Haven't tried it but it might work.