How to close the parent window from its child?

I have the following case:

I have a gridview on my page :

page1.aspx

I open another page(page2.aspx) through that gridview in a rad window then after that,through some button on page2.aspx i open the last page (page3.aspx) in a rad window also.

all these steps are performed through server side code :

 protected void OpenNewWindow(string url, int width, int height, int mode)
        {
            RadWindow newWindow = new RadWindow();
            newWindow.NavigateUrl = url;
            newWindow.VisibleOnPageLoad = true;
            newWindow.KeepInScreenBounds = true;
            newWindow.Skin = "Metro";
            if (width > 0)
            {
                newWindow.Width = width;


            }
            if (height > 0)
            {
                newWindow.Height = height;
            }
            newWindow.VisibleStatusbar = false;
            if (mode == 0)
            {
                {

                }
                //newWindow.OnClientClose = "OnChildWindowClosed";
                newWindow.DestroyOnClose = true;
                newWindow.InitialBehaviors = WindowBehaviors.Maximize;
            }
            RadWindowManager1.Windows.Add(newWindow);
        }

What i want to do is :

when clicking on a specific button on my (page3.aspx) close it and its parent page2.aspx.

How to do this (server side)?

I try this :but it just closes the child page3.aspx i want to close the parent page2.aspx also ?!

  protected void Button1_Click(object sender, EventArgs e)
        {
            ((RadAjaxManager)this.Parent.FindControl("RadAjaxManager1")).ResponseScripts.Add("CloseModal();");