private void btTaoTaiKhoan_Click(object sender, EventArgs e)
        {
            frmTiepNhanTaiKhoan fTNTK = new frmTiepNhanTaiKhoan(txtMaHopDong.Text);

            fTNTK.Show();
            fTNTK.FormClosed += FTNTK_FormClosed;
        }
        private void btThem_Click(object sender, EventArgs e)
        {
            frmTiepNhanTaiKhoan fTNTK = new frmTiepNhanTaiKhoan();

            fTNTK.Show();
            fTNTK.FormClosed += FTNTK_FormClosed;
        }