private void cmdAddProduct_Click(object sender, RoutedEventArgs e)
        {
            Boolean result = CHelper.ValidateLookup(lblCustomer, uCustomer, false);

            if (!result)
            {
                return;
            }

            populateExcludeDocSet();

            CCriteriaBillSummaryItem cr = new Criteria.CCriteriaBillSummaryItem();

            cr.SetActionEnable(false);
            cr.SetDefaultData(vw);
            cr.Init("1");

            WinMultiSelection w = new WinMultiSelection(cr, CLanguage.getValue("bill_summary_item"));

            w.ShowDialog();

            if (w.IsOK)
            {
                vw.AddAccountDocReceipts(convertToReceiptItem(w.SelectedItems));
                calculateReceiptTotal();
                vw.IsModified = true;
            }
        }