Drupal 6: Setting custom breadcrumb and primary navigation to active for any page

function mymodule_preprocess_page(&$variables){
  $breadcrumb = mymodule_custom_breadcrumb($variables);
  if($breadcrumb){
    $variables['breadcrumb'] = $breadcrumb;
  }
}
 
 
function mymodule_custom_breadcrumb($variables){
  // taxonomy term page
  if(arg(0) == 'taxonomy' and arg(1) == 'term' and is_numeric(arg(2))){
    $term_obj = taxonomy_get_term(arg(2));
 
    if($term_obj->vid == 1){
      $parents = taxonomy_get_parents($term_obj->tid);
      foreach ($parents as $parent_obj){
        $breadcrumb[] = l($parent_obj->name, taxonomy_term_path($parent_obj));
      }
    }
 
    $breadcrumb[] = l(t('foobar'), 'foobar');
  }
 
  if($breadcrumb){
    $breadcrumb[] = l(t('Home'), NULL);
    $breadcrumb = array_reverse($breadcrumb);
    menu_set_active_item('foobar');
    return theme('breadcrumb', $breadcrumb);
  }
}