Destroying blocks

I got a script for destroying blocks in FPS and wanted to limit the destroying range. But it doesnt work, the string doesnt change.`using System.Collections; using System.Collections.Generic; using UnityEngine;

public class harvest : MonoBehaviour {

 public string lootMats = "rock";
 public int howMuchLoot = 0;
 public string withinRange = "no";
 public Transform rockSys;
 public int durabilityVal = 3;
 

 // Use this for initialization
 void Start()
 {



 }

 // Update is called once per frame
 void Update()
 {

 }

 void OnMouseDown()
 {
     if (withinRange == "yes")
     {

     Debug.Log(lootMats + "  " + howMuchLoot);

     Destroy(gameObject);

 }
 }


 void OnTriggerEnter(Collider other)
 {

     withinRange = "yes";

 }

 void OnTriggerExit(Collider other)
 {

     withinRange = "no";

 }

} `