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

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

public class RotatableObject : MonoBehaviour
    {
        private void RotateAccordingTo(Hand hand)
        {
            Quaternion desiredRotation = hand.CurrentRotation;
            desiredRotation.y = 0;
            desiredRotation.z = 0;
            this.transform.localRotation = desiredRotation;
        }
    }

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

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

could be it.