Ну, можно вот так извратиться:
[CODE]$arElementID = array();
$res = CIBlockElement::GetList(
false,
$arFilter,
false,
array('nTopCount' => 40),
array('ID')
);
while ($el = $res->Fetch())
$arElementID[] = $el['ID'];
if (count($arElementID))
$arFilter['ID'] = $arElementID;
$res = CIBlockElement::GetList(
$arOrder,
$arFilter,
false,
array('nPageSize' => 20),
$arSelect
);
[/CODE]