private void btnCreateCustomsInvoice_Click(object sender, EventArgs e)
        {
            if (txtInvoiceNumber.Text.Trim() == "")
            {
                MessageBox.Show("Please enter an Invoice number");
                return;
            }

            if (txtNumberOfCases.Text.Trim() == "")
            {
                MessageBox.Show("Please enter Number of Cases");
                return;
            }

            if (txtTotalWeight.Text.Trim() == "")
            {
                MessageBox.Show("Please enter Weight");
                return;
            }

            try
            {
                int salesOrder = Convert.ToInt32(txtInvoiceNumber.Text.Trim());
            }
            catch (InvalidCastException)
            {
                MessageBox.Show("Please enter numbers only in the Invoice number textbox");
                return;
            }
            try
            {
                InvoiceHelper invoiceHelper = new InvoiceHelper(SessionManager.NewQBSession());
                Invoice       invoice       = invoiceHelper.Populate(txtInvoiceNumber.Text);

                ExcelExportCanadaCustomsInvoice exporter = new ExcelExportCanadaCustomsInvoice(invoice,
                                                                                               Convert.ToDouble(txtTotalWeight.Text),
                                                                                               Convert.ToInt64(txtNumberOfCases.Text));
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message, "Error in Program", MessageBoxButtons.OK, MessageBoxIcon.Information);
            }
        }