If you are using platform movement then it can be changed at the events and setting the default control to no.Then at events you will do something like this.player D key down/set animation to duck or whatever it has to be.There's also a simulate left,right and jump option for the platform movement behavior.Would look something like this.Player s key down/Simulate pressed Right.Same goes for left and jump.
I can make a demo capx for you if you want.