vtkSeedWidget vtkSeedRepresentation avoid right click

How can I avoid right click event on a vtkSeedWidget / vtkSeedRepresentation ?
I have tried:

	vtkSeedWidgetCallback* pCallback = vtkSeedWidgetCallback::New();
	m_pSeed->AddObserver(vtkCommand::PlacePointEvent, pCallback);
	m_pSeed->AddObserver(vtkCommand::InteractionEvent, pCallback);

but on the right click is called vtkSeedWidget::CompleteInteraction wich stop the planting of seeds … I want to stop the user to give up planing seeds until the number of seeds is 5.