@andromeda- You are in luck. The Phalaenopsis orchid is the most commonly re-blooming flower spike among orchids. If your plant has reached 12 or more inches, you can cut it half way back above one of the small notches on the flower spike.
To keep your orchids growing well, you should only do this once per flower spike. Otherwise, you will end up with fewer flowers. You can also completely cut off the flower spike. Your orchid will have more energy to more flowers on a new flower spike.