How to ONLY allow user to rotate a game object clockwise?

I have a game object which can be rotated by the user:

Code (csharp):

1. public class RotatableObject : MonoBehaviour
2.     {
3.         private void RotateAccordingTo(Hand hand)
4.         {
5.             Quaternion desiredRotation = hand.CurrentRotation;
6.             desiredRotation.y = 0;
7.             desiredRotation.z = 0;
8.             this.transform.localRotation = desiredRotation;
9.         }
10.     }    

Right now, the user is able to rotate it both counter-clockwise and clockwise.

I wish to modify the code so that the object does not rotate when the user tries to turn it counter-clockwise. It rotates only when the user is turning it clockwise.

How can I achieve this effect?

 

Not sure if i get you right but

Code (CSharp):

1.     if(desiredRotatio.eulerAngles.y < this.transform.rotation.eulerAngles.y)//could be the wrong axis
2.             return;

could be it.