Double Click problems with NGUI?

Here is the I made. I have tested it with a NGUI button.

In the inspector :

 using UnityEngine;
 using System.Collections;
 
 public class DoubleClick : MonoBehaviour
 {
     public float delayBetween2Clicks ; // Change value in editor
     private float lastClickTime = 0 ;
     
     public void OnClickCallBack()
     {
         if( Time.time - lastClickTime  < delayBetween2Clicks )
         {
             Debug.Log( "Double clicked" );
         }
         else
         {    
             StartCoroutine( OnClickCoroutine() ) ;    
         }
         lastClickTime = Time.time ;
     }
 
     IEnumerator OnClickCoroutine()
     {    
         yield return new WaitForSeconds( delayBetween2Clicks ) ;
     
         if( Time.time - lastClickTime  < delayBetween2Clicks )
         {
             yield break ;
         }
 
         Debug.Log( "Simple click" );
     }
 
 } // class DoubleClick