docking pane do NOT tab

I think I know half the problem. The following code prevent the pane attaching to other pane. But I have not figured out how to prevent other panes attaching into the pane.

if (wParam == XTP_DPN_ACTION)
 {
  XTP_DOCKINGPANE_ACTION* pAction = (XTP_DOCKINGPANE_ACTION*)lParam;

    if (pAction->action == xtpPaneActionAttaching)
  {
   if (pAction->pPane->GetID() == IDR_PANE_TEST_CTRL/*the pane I want to be stand alone*/)
   {
    pAction->bCancel = TRUE;
   }
  }

  return TRUE;
 }