-- begin update for first part of two-part refresh --
    BeginUpdate(my_layer);
    -- do some refresh, but not all --
    my_partial_refresh_routine(my_layer);
    -- end update, false (not completely done refreshing yet) --
    EndUpdate(my_layer, FALSE);
    -- begin update for last part of refresh --
    
BeginUpdate(my_layer);
    -- do rest of refresh --
    my_complete_refresh_routine(my_layer);
    -- end update, true (completely done refreshing now) --
    EndUpdate(my_layer, TRUE);