Making spell invisible

Making spell invisible

I have a spell that uses windwalk on the death of a unit. This is working fine but I have to attach wind walk onto my hero, this would mean that people can click on it to get the wind walk effect so i would like to have it "invisible" so the player cant click it.

event
a unit dies
condition
killing unit = hero
action
add windwalk to hero
order hero to windwalk
wait 0.2 seconds
remove windwalk