function views_itunes_views_feed_argument($op, &$view, $arg) {
  if ($op == 'argument' && $arg == 'feed') {
    $view->page_type = 'views_itunes';
  }
  else if ($op == 'post_view') {
    $args = views_post_view_make_args($view, $arg, 'feed');
    $url = views_get_url($view, $args);
    $title = views_get_title($view, 'page', $args);

    drupal_add_link(array('rel' => 'alternate',
                          'type' => 'application/rss+xml',
                          'title' => check_plain($title),
                          'href' => url($url, drupal_query_string_encode($view->used_filters), NULL, TRUE)));
    if ($view->build_type != 'block') {
      return theme('feed_icon', url($url, drupal_query_string_encode($view->used_filters)));
    }
  }
}