function mypagetitle_nodeapi(&$node, $op, $teaser = NULL, $page = NULL) {
  switch($op) {
    case 'view':
      mypagetitle_set_title('testing...');
      break;
  }
}

function mypagetitle_set_title($title = NULL) {
  static $stored_title;

  if (isset($title)) {
    $stored_title = $title;
  }
  return $stored_title;
}