How to make unit unselectable

when a player STILL has control.. (so he can select other units and bring up the money and stuff) how can you make a unit unselectable?

im sorry if im using the wrong words (i got the polisch version)
there is a unit statistic , selection scale or something like that , set that to zero
im not sure that works

There is a setting, I forget what it is called, but it is done via a trigger. also if you assign "carrion swarm" to a unit that also works, if a bit crude.

If you have WE unlimited, and you activate the advanced triggers, they also have a more clearly labled version of the trigger if you absolutely can't find it (sorry I can't give more info but I just quit out of my map and im too lazy to look upt he exact trigger name)

a unit can be made unselectable by giving it the "locust" ability (that's the ability the units summoned by the crypt lord's ultimate have). Note that a unit with locust is also untargetable, meaning it's also unkillable, and it doesn't show on the minimap.

i cannot set the select scale to 0... only to .1

Forget the selection scale. It only tells the game how big the selection circle must be. The unit is still selected when you click on it's model.