Give the actors a variable called pause. Initialize it to 1 when the actor is created. Then you use a keypress event with that actor. when the key is pressed, set the pause variable to 0 or set it to 1 if it is already 0.
In the code where the actors velocity is set multiply the velocity by pause. If the actor does anything like shooting, check pause before allowing that.
It works just like the variable that prevents someone from jumping twice in the air.
Read my post here for a better idea of how to make it work.
http://game-editor.com/forum/viewtopic. ... eld+sheild