Tell them their bat's edges aren't 40mm. That'll upset them - trust me.
Jokes aside, why are you trying to disrupt the batsman's concentration with the field? There are things you can do I guess to change the rhythm up a bit, like slow things right down when they're scoring quickly, get the ball back to the bowler ASAP when they're dotting it up and get through the overs quickly, but things like changing the field is entirely dependent on the bowler executing a plan, and also on the type of batsman you're bowling to...