cell_renderer_time_delta = Gtk::manage( new CellRenderer_Time() );
column->pack_start(*cell_renderer_time_delta,true);
column->add_attribute(cell_renderer_time_delta->property_time(), model.time_delta);
cell_renderer_time_delta = Gtk::manage( new CellRenderer_Time() );
column->pack_start(*cell_renderer_time_delta,true);
column->add_attribute(cell_renderer_time_delta->property_time(), model.time_delta);