def goto_prev_selection
      return if selected_rows().length == 0 
      row = selected_rows().sort{|a,b| b <=> a}.find { |i| i < @obj.current_index }
      row ||= @obj.current_index
      #@obj.current_index = row
      @obj.goto_line row
    end
def goto_prev_selection
      return if selected_rows().length == 0 
      row = selected_rows().sort{|a,b| b <=> a}.find { |i| i < @obj.current_index }
      row ||= @obj.current_index
      #@obj.current_index = row
      @obj.goto_line row
    end
after selecting, traverse selections backward