How do I make an attack (or something else) pressing two different keyboard keys?

There is a Normal Attack when I press the key X, a Dash when I press the key Space.

I want to make an new Special Attack when I press the X and Space together.

I am working on it for a while and couldn't figure it out.

I still trying. Any help will be welcome.

When you press one of the keys, start a short timer. If the other key is pressed before timer hits 0, then perform the attack. If the key is pressed outside of the timer (too slow) then you would just see the normal attack for that key.