Stop units from attacking wards?

Okay I am having a problem, I can't seem to get my units to stop being able to attack wards. The attack doesn't have ward checked as attackable, is there something else I need to select or something? I am just not understanding y it isn't working. :(

y dont u make the ward invincable or have a large hitpoint base

It's not actually a ward, its a unit that I want certain things not to attack, but others to be able to, it just has the ward tag.

what about making triggers for it like
unit attacks(ward)

unit = to what u dont want to hit it

order unit to stop attack