protected void Page_Load(object sender, EventArgs e)
        {
            NVPAPICaller payPalCaller = new NVPAPICaller();
            string retMsg = "";
            string token = "";

            if (Session["payment_amt"] != null)
            {
                string amt = Session["payment_amt"].ToString();

               bool ret = payPalCaller.ShortcutExpressCheckout(amt, ref token, ref retMsg);
              //  bool ret = true;
                if (ret)
                {
                    Session["token"] = token;
                    Response.Redirect(retMsg);
                }
                else
                {
                    Response.Redirect("CheckoutError.aspx?" + retMsg);
                }
            }
            else
            {
                Response.Redirect("CheckoutError.aspx?ErrorCode=AmtMissing");
            }
        }