function handleEshopFrontFilter($name, array $aEvent, $handlerModId, $srcModId) {
    if(
        $aEvent['mod_id'] == 'eshop_item' &&
        $aEvent['sql_prefix'] == 'i.' &&
        in_array(
            $aEvent['viewType'],
            array(
                'body_items',
                'body_urgent_items',
                'body_filtered',
                'body_search'
            )
        )
    ) {
        $aEvent['sql_part'] .= 'AND i.custom_field_XXX = "RU"';
    }
    return $aEvent;
}