private void btnCross_Click(object sender, EventArgs e)
        {
            btnNew.PerformClick();
            this.Visible = false;
            SalesmanManager m = new SalesmanManager();

            m.Visible = true;
        }
        private void pbSalesmen_Click(object sender, EventArgs e)
        {
            pnlMain.Controls.Clear();
            SalesmanManager salm = new SalesmanManager();

            salm.TopLevel        = false;
            salm.Dock            = DockStyle.Fill;
            salm.FormBorderStyle = FormBorderStyle.None;
            pnlMain.Controls.Add(salm);
            salm.Show();
        }