How do I check a players armor slots for an entitys AI-condition?

Hi, 

I am completely new here, started modding literally today. I have modded an entity by now and want it to only attack me if I am not wearing a special hat. I tried: 

If [get item from armor slot [3] of [Event/target entity] = *special hat] do [...] 

and it does not work. Is slot 3 the wrong one for helmets or am I as player not the Event/target entity?

Please help :(

~Stella