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: (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 = 1 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