C# How to Drag and Scale with Mouse Window

I'm trying to make the example in the Unity 3d documentation drag and scale with the mouse.But I can't find anything in the documentation for GUI.Window that mentions how to do that. Do you guys know how?

 using UnityEngine;
 using System.Collections;
 
 public class Example : MonoBehaviour {
     public Rect windowRect = new Rect(20, 20, 120, 50);
     void OnGUI() {
         //Trying to make GUI.Window move and scale
         windowRect = GUI.Window(0, windowRect, DoMyWindow, "My Window");
     }
     void DoMyWindow(int windowID) {
         if (GUI.Button(new Rect(10, 20, 100, 20), "Hello World"))
             print("Got a click");
         
     }
 }