Question on how to add a double jump and eventually a wall dodge

What would be the proper way to check if the jump key was pressed again while in the air? Adding the boolean check to ::OnStartJump() fires both the first and second jump with one press.

EDIT: On second thought, if I wanted to be able to have more control while in the air (as in starting the jump while moving backwards, then changing direction to go forward mid jump) would it be worth dropping the ::OnStartJump() and just make my own jump function by modifying the velocity? Or would it still be better to use that?