function IsUserNameUnique(field, id, username)
  {
    $.post("/index.php", {'initialize_for_ajax' : 'true', 'file': './scripts/components/system/users/mods/mod_unique_username.php', 'user_username': username, 'user_id': id}, function(data)
    {
      if(data.result == false) {FocusTabField(field);inlineMsg(field,data.alert,2);return false;}
    }, "json");
  }