You probably have two variables on your player. One called "DoublePunch" and another one called "DoublePunch_Toggled" or something like that.
So,
When A is pressed:Â Â Â (Punch)
                               Set DoublePunch to 1
When A is pressed     Set DoublePunch_Activated to 1
DoublePunch is = 1
When A is Pressed
DoublePunch_Toggled = 1 (Double Punch)
                                        Set DoublePunch to 0
                                        Set DoublePunch_Toggled to 0
Now you can Double Punch, but you can also do it after 200-300 ms.
So, you need to add a "Wait" action when A is pressed:
When A is pressed: (Punch)
DoublePunch = 1Â Â Â Â Â Â Wait 200/300 ms
                                Set DoublePunch_Activated to 0
                                Set DoublePunch to 0
I am not sure if this will work, try it.
And maybe upload a .capx, if it doesnt work!
-CX05