Build a fake typing app

I need a program built asap where someone can hit any key on a keyboard and our preset text appears on the screen. This is for a show we are making. An actor is typing a script on a macbook air. We want to give the illusion that the actor is typing the text but really they will just be hitting random keys on the keyboard as the correct text appears on the screen. We have the artwork and text ready to go. I will need you to sign an NDA, I need this on a very shoer turnaround, hours, the scene plays first thing in the morning. I know that is a lot to ask but perhaps someone can help us.