Make flying my character

I’am french i sorry for my bad english, but I have a problem : I want my character flys when I press the space bar and back down when i don"t press space bar, so I make this blueprint

But when i clic on “Play” my character already flies ^^ and that’s when I press the spacebar my character backdown.
I just want when i press space bar my character get value on the Z axis to up.