What exactly is the effect you're looking for? Do you want the actor to literally be pulled back ? A good actor can act the part of being pulled back. Is the wall an existing wall that you can't mess with or are you building the wall for the haunt? If you are building it, the setup is simple. The bungee can be a long cloth tube with a clothes line inside of it. One end of line attaches to actor. The line goes through cloth tube, through a small hole in wall, around a pulley and attaches to a weight. As actor goes toward crowd, weight comes up. As actor gets "pulled" back, he walks backward to wall and pulley goes to floor. If the distance is far, use 2 pulleys. The first pulley sends the line up to the second pulley mounted high, then down to floor. This way the actor can go as far as the height you mount the second pulley. Have the connector of fake bungee attach to wall via an open eyehook. The cloth tube is glued, sewn etc. to the bungee connector loosely so the clothes line can pass freely out of tube, through eyehook, then into hole in the wall. This will guide the line without roughing up the line or wearing the hole in wall bigger. The cloth tube will need to be as long as the distance the actor will be going forward. As the actor goes backward, the cloth tube will bunch up between him and the wall, kinda like elastic band in a pair of sweat pants. Save some of the paint for the wall to color the clothes line. Use latex paint, dilute it with water, and dye the clothes line. That way it will be less visible going through the eyehook and into the wall.