GUI Button to replace a click on a waypoint in 2D pathfinding

I am creating a 2D pathfinding system for indoor navigation, and I am trying to create a GUI button that not only goes to the scene of the floor with the waypoints, but it also replaces what would have been a click on a specific waypoint, e.g. waypoint18, to enable an object navigate to that location.

This is the code i have at the moment;

using UnityEngine; using System.Collections;

public class Try : MonoBehaviour {

 public Waypoint exitPoint;
 public AI_Pathfinder ap;
 
 void Start () {
           }
 
 void Update () {
            }

 private void OnGUI()
 {
     if(GUI.Button(new Rect(15,15,100,50), "Waypoint18"))
     {
    Application.LoadLevel("GroundFloor");
        ap.nextWP = exitPoint;
     }  
  }

}

What should i add? Any help is appreciated. Thanks.