CUserTypeWebdavElement::OnBeforeSave

function OnBeforeSave($arUserField, $value)
{
	if(isset(static::$UF_TO_DELETE[$value]))
	{
		//delete this UF.
		return '';
	}

	$value = intval($value);

	if ($value > 0)
	{
		if (isset(static::$UF_MOVED[$value]))
			$value = static::$UF_MOVED[$value];
	}
	else
	{
		$value = '';
	}

	return $value;
}