private void btnbill_Click(object sender, EventArgs e)
        {
            ApplicationDesign.SetSubSubButtonDesign(ref sender);

            frmPurchasebillingwindow                 = new PurchaseBillingWindow();
            frmPurchasebillingwindow.WindowState     = FormWindowState.Maximized;
            frmPurchasebillingwindow.FormBorderStyle = FormBorderStyle.None;
            frmPurchasebillingwindow.TopLevel        = false;

            currentForm = frmPurchasebillingwindow;
            frmPurchasebillingwindow.Size = pnlWindow.Size;
            pnlWindow.Controls.Clear();
            pnlWindow.Controls.Add(frmPurchasebillingwindow);
            frmPurchasebillingwindow.Show();
        }
        private void btnAdvancePayment_Click(object sender, EventArgs e)
        {
            ApplicationDesign.SetSubSubButtonDesign(ref sender);

            AdvancePaymentList frmAdvanceReceiptList = new AdvancePaymentList();

            //frmAdvanceReceiptList = new NoteAndVoucherList();
            frmAdvanceReceiptList.WindowState     = FormWindowState.Maximized;
            frmAdvanceReceiptList.FormBorderStyle = FormBorderStyle.None;
            frmAdvanceReceiptList.TopLevel        = false;

            currentForm = frmAdvanceReceiptList;
            frmAdvanceReceiptList.Size = pnlWindow.Size;
            pnlWindow.Controls.Clear();
            pnlWindow.Controls.Add(frmAdvanceReceiptList);
            frmAdvanceReceiptList.Show();
        }