Change the value of a piece of content using a comment
Assuming your content type is called your_content_type and your module is called yourmodulename, you can use the following code:

It will set some state when a none-priviledged user posts a comment, and show a state selection UI for priviledged users. The state will be saved to the CCK field_erledigt_warten in the node in either case.

&lt;?php
/**
 * Implementation of hook_comment().
 * Fill a CCK field  in Drupal 6
 */
function yourmodulename_comment(&amp;$comment, $op) {
  global $user;

  if (is_array($comment)) {
    $node = node_load($comment['nid']);
  }
  else {
    $node = node_load($comment-&gt;nid);
  }

  if ($node-&gt;type == 'your_content_type') {
    switch ($op) {
      case 'insert':
      case 'update':
        if (user_access('edit field_erledigt_warten')) {
          // QD-Mitarbeiter
          if (isset($comment['field_erledigt_warten']) &amp;&amp; $comment['field_erledigt_warten']) {
            if ($node-&gt;field_erledigt_warten[0]['value'] != $comment['field_erledigt_warten']) {
              $node-&gt;field_erledigt_warten[0]['value'] = $comment['field_erledigt_warten'];
              drupal_set_message(t('Status wurde auf %v ge&amp;auml;ndert.', array('%v' =&gt; $comment['field_erledigt_warten'])));
              node_save($node);
            }
          }
        } else {
          // Kundenaccount
          $node-&gt;field_erledigt_warten[0]['value'] = 'neu';
          node_save($node);
        }
        break;
    }
  }
}

/**
    Implementation of hook_form_alter
 * Add a input box to the comment form
 */
function yourmodulename_form_alter(&amp;$form, $form_state, $form_id) {
  if ($form_id == 'comment_form') {
    if (is_array($form) &amp;&amp; isset($form['nid']) &amp;&amp; is_array($form['nid'])) {
      $node = node_load($form['nid']['#value']);
    }
    if (isset($node) &amp;&amp; is_object($node) &amp;&amp; isset($node-&gt;type) &amp;&amp;
      $node-&gt;type == 'your_content_type' &amp;&amp; user_access('edit field_erledigt_warten')) {
      $states = array_flip(array('some', 'values', 'come', 'here'));
      foreach($states as $text=&gt;$index) $states[$text] = $text;
      $status = $node-&gt;field_erledigt_warten[0]['value'];
      $form['field_erledigt_warten'] = array(
        '#type' =&gt; 'select',
        '#title' =&gt; 'neuer Status dieser Forumseite',
        '#default_value' =&gt; $status,
        '#options' =&gt; $states,
      );
    } 
  }
}