Disable field in Sales Orders SO301000 Screen

Hi Expert.

I try disale field So Notes depends on the condition of the shipment  in below:

I try set break point at:

PXUIFieldAttribute.SetEnabled(cache, row, true);

                        PXUIFieldAttribute.SetEnabled<SOOrderExt.usrSoNote>(cache, row, true);

break point ok, program touch here.

 protected void SOOrder_RowSelected(PXCache cache, PXRowSelectedEventArgs e, PXRowSelected InvokeBaseHandler)

        {

            InvokeBaseHandler?.Invoke(cache, e);

            var row = (SOOrder)e.Row;

            if (row != null && row.OrderNbr != null)

            {

                Base.Document.Cache.AllowUpdate = true;

                Base.Transactions.Cache.AllowUpdate = true;

                SOOrderShipment ship = PXSelect<SOOrderShipment, Where<SOOrderShipment.orderNbr, Equal<Required<SOOrderShipment.orderNbr>>>>.Select(Base, row.OrderNbr.Trim());

                if (ship != null && ship.ShipmentNbr != null)

                {

                    SOShipment shipment = PXSelect<SOShipment, Where<SOShipment.shipmentNbr, Equal<Required<SOShipment.shipmentNbr>>>>.Select(Base, ship.ShipmentNbr.Trim());

                    if (shipment != null && shipment.Status != null && !ConstantsSO.SHIP_STATUS_OPEN.Equals(shipment.Status))

                    {

                        PXUIFieldAttribute.SetEnabled(cache, row, false);

                        PXUIFieldAttribute.SetEnabled<SOOrderExt.usrSoNote>(cache, row, false);

                    }

                    else

                    {

                        PXUIFieldAttribute.SetEnabled(cache, row, true);

                        PXUIFieldAttribute.SetEnabled<SOOrderExt.usrSoNote>(cache, row, true);

                    }

                }

                else

                {

                    PXUIFieldAttribute.SetEnabled(cache, row, true);

                    PXUIFieldAttribute.SetEnabled<SOOrderExt.usrSoNote>(cache, row, true);

                }

            }

        }

but this field still enable

Can you help me? Thank you so much.