I did that with a simple variable.
For example, you want to dash and stop walking if you hit left twice:
if press Left
{if variable "dash"=0
{dash=30; and here put your stuff for walking}
if variable dash>0
{Here your stuff for dashing, like Megaman fore example}
}
That´s the basic routine when you press Left key, now you need COUNTDOWN for the variable name DASH the one that let you know if you hit the key or not, so go to "Every tick" and:
if dash>0 {dash -=1;} -----> this substract 1 from "dash" and make it zero, so if you dont press Left key in that time, you wont be able to dash....
I won´t attach a Construct 2 example here, but you can see what Ive done in my game.
Hope that helps