I do this without keyclone with a simple cast sequnece macro: (well keyclone passes the keys like normal, just bind all of these to the same key on all 3 toons)

Priest 1 first click it will fear second and third it will do nothing

/castsequence reset=24 psychic scream, ,

Lock1 second click this one will work

/castsequence reset=24 , howl of terror ,

Lock2 third for this


/castsequence reset=24 , , howl of terror

if you get the idea just modify it around a bit to get what you need. A comma in a castsequence works if there is a spell inbetween it or not.