See Chapter 15, Label Builder.
ModLabelData *tsol_lbuild_create(Widget widget, void (*event_handler)() OK_callback, ..., NULL); void tsol_lbuild_destroy(ModLabelData *lbdata); XtPointer tsol_lbuild_get(ModLabelData *lbdata, ..., NULL); void tsol_lbuild_set(ModLabelData *lbdata, extended_operation, NULL);