public function replaceValue($fieldName, $oldvalue, $newvalue)
    {
        $result = $this->row[$fieldName];
        if (!is_array($result)) {
            if ($oldvalue == $result) {
                $this->row[$fieldName] = $newvalue;
                $this->informChanges();
            }
        } else {
            for ($i = count($result) - 1; $i >= 0; $i--) {
                if ($result[$i] == $oldvalue) {
                    $this->row[$fieldName][$i] = $newvalue;
                    $this->informChanges();
                }
            }
        }
    }