private void cmbTen_tt_SelectedIndexChanged(object sender, EventArgs e)
 {
     m_NhanVienCtrl.KichHoatTextBox(txtTen);
     if (cmbTen_tt.Text == "Bỏ Qua")
     {
         m_NhanVienCtrl.KhongKichHoatTextBox(txtTen);
     }
 }