Something

function naf_form_order_form_alter($form_id, &$form) {
  // Is this a CCK node form?
  if (preg_match('/^content-(.*?)_node_form$/', $form_id, $match)) {
    $type = $match[1];
    if (function_exists('theme_content_'. $type .'_node_form')) {
      // If custom theme function exists, assign it to the form
      $form['#theme'] = 'content_' .$type. '_node_form';
    }
  }
}