id свойства 31, свойство множественное
AddEventHandler("iblock", "OnBeforeIBlockElementAdd", Array("MyClass", "OnBeforeIBlockElementAddHandler")); class MyClass { // создаем обработчик события "OnAfterIBlockElementAdd" function OnBeforeIBlockElementAddHandler(&$arFields) { if($arFields["IBLOCK_ID"] == 14){ // dbg($arFields,true); foreach($arFields[PROPERTY_VALUES][31] as &$file): CAllFile::ResizeImage( $file, array("width" => "200", "height" => "200"), BX_RESIZE_IMAGE_PROPORTIONAL); endforeach; } } }