How to loop just a certain part of an animation?

I have made a crouching animation and exported it as .fbx to Unity, and it is an animation of a character that stands up straight, and than goes to a crouching position. In Unity, I want mecanim to play the part where he goes FROM standing up straight, to the crouch position (frame 1 to 15), and then loop the part of the animation where he is IN the crouch position (frame 15 to 79). How can I achieve this and play frams 1 to 15 just once, and then loopframe 16 to 79. Thanks a lot!