OnMouseDown transform problem

Hi I'm trying to make a code so that if an object is clicked, it will slide towards another object. Slide the whole way there, not one inch closer every time I click the object.

This is my script using UnityEngine; using System.Collections;

  public class OnMouseDownWolf : MonoBehaviour {
     public Transform target;
     public float speed;
     void Update(){
         if (Input.GetMouseButtonDown(0))
         {
         float step = speed * Time.deltaTime;
         transform.position = Vector3.MoveTowards(transform.position, target.position, step);
         }    
         }
     }

So far the object will move 1 inch towards to target everytime I click said object. But I'd like it so that when I click the object, it will slide the whole way there.

Thank you.