How to prevent the player's spaceship to throw a missile when the text object indicate "Missles: 0"?

I have included a code where the player can press "CTRL" to make his spaceship throw a missile. But when the text object (txtMissiles) indicate "Missile: 0", I want the player to not be able to throw missiles anymore. How can I realize that?

This is a picture that represents what I did:

Just use a second condition on ctrl pressed

Number of Missels > 0

To klabundee:

Thank you! It works!