code: private void doChangeSelectionInList(int moveBy)
  	{
  		PlayListEntry [] selected = playList.getSelectedEntries();
  		if (selected==null || selected.length == 0)
  		{
  			playList.setSelectedElement(0);
  			doMakeIndexVisible(0);
  		}
  		else
  		{
  			int firstIndex = selected[0].getIndexInPlaylist(); 
  			int lastIndex = selected[selected.length - 1].getIndexInPlaylist();
  			if (moveBy < 0)
  			{
  				firstIndex += moveBy;
  				if (firstIndex<0) firstIndex = 0;
  			}
  			else
  			{
  				lastIndex += moveBy;
  				if (lastIndex >= playList.size()) lastIndex = playList.size() - 1; 
  			}
  			playList.setSelectedElements(firstIndex, lastIndex);
  			if (moveBy < 0) doMakeIndexVisible(firstIndex); else doMakeIndexVisible(lastIndex);
  		}
  	}
docs: Expands the selection (moving cursor with shift)
  @param moveBy
  @since 15.12.2011