Cannot call modal pop up in authenticate

Hi I want to call the modal pop up after the login control authenticate. I tried to put it inside the event but still doesnt work here  is my code:

protected void Login1_Authenticate(object sender, AuthenticateEventArgs e)
        {

          //sql statement
           if(user!=null)
            {
 
                e.Authenticated = true;
                if (Login1.RememberMeSet == true)
                {
                    Response.Cookies["UserName"].Expires = DateTime.Now.AddDays(30);
                    Response.Cookies["Password"].Expires = DateTime.Now.AddDays(30);

                }
                else
                {
                    Response.Cookies["UserName"].Expires = DateTime.Now.AddDays(-1);
                    Response.Cookies["Password"].Expires = DateTime.Now.AddDays(-1);

                }
                Response.Cookies["UserName"].Value = Login1.UserName.Trim();
                Response.Cookies["Password"].Value = Login1.Password.Trim();
                Session["login"] = User.Identity.Name;
                ModalPopupExtender1.Show();
            }
}