How to change an input variable?

I have a block that represents a button (right now it is just a constant block - when it is 1 it is ON and when it is 0 it is OFF. But it will change to something dynamic when my model is complete).

I want to input that button in a stateflow chart and have a state in the stateflow chart that has two substates showing if the button is ON or OFF. Eventually I may have other states in this stateflow chart that automatically turns the system ON, so I would like to update my button input accordingly, but as far as I know there is no way to change an input variable in stateflow, so I would like some suggestions on how to implement this.

[liu zhe]

You could combine two constant blocks with Manual Switch,with one constant block input 1 and other constant block input 0,and you can switch them by switch(double -click the block).The model is just like the picture showing.