private class MyTableViewer extends TableViewer {
    public MyTableViewer(Composite parent) {
      super(parent);
    }

    @Override
    protected Object[] getSortedChildren(Object parent) {
      Object[] finalElements = super.getSortedChildren(parent);
      // do your calculations on the elements or inform an event handler
      return finalElements;
    }
  }

public class TableViewerSendingContentChangedEvent extends TableViewer {
	
	protected EventListenerSupport<ChangeListener> eventHandler;
	/**
	 * Calls only the super constructor
	 * 
	 * @param parent
	 * @param style
	 * 
	 * @see org.eclipse.jface.viewers.TableViewer.TableViewer(Composite parent, int style)
	 */
	public TableViewerSendingContentChangedEvent(Composite parent, int style) {
		super(parent, style);
		eventHandler = EventListenerSupport.create(ChangeListener.class);
	}
	
	/*
	 * (non-Javadoc)
	 *
	 * @see org.eclipse.jface.viewers.StructuredViewer#internalRefresh(java.lang.Object)
	 */
	protected void internalRefresh(Object element) {
		super.internalRefresh(element);
		eventHandler.fire().stateChanged(new ChangeEvent(this));
	}
	
	public void addRefreshListener(ChangeListener aApp) {
		eventHandler.addListener(aApp);
	}
}