[Sunka]

If could help...
This code (and only this code) is used in phpBB forum for that...
Maybe that would help to create same MOD for vBulletin

PHP Code:

if($post_mode == 'edit_last_post' || $post_mode == 'edit_topic')
           {
                   $sql_update_posts = 'UPDATE ' . POSTS_TABLE . '
                                     SET post_time = ' . $current_time . '
                                     WHERE post_id = ' . $data['post_id'] . ' 
                                              AND topic_id = ' . $data['topic_id'];
                   $db->sql_query($sql_update_posts);
   
                   $sql_update_topics = 'UPDATE ' . TOPICS_TABLE . ' 
                                     SET topic_last_post_time = ' . $current_time . ' 
                                     WHERE topic_id = ' . $data['topic_id'];
                   $db->sql_query($sql_update_topics);            
           
                   update_post_information('forum', $data['forum_id']);
                   markread('post', $data['forum_id'], $data['topic_id'], $data['post_time']);
           }