New Post: Undefined Index Classes/PHPExcel/Calculation/LookupRef.php on line 641

Good Day

Theres a problem when im running this formula

=INDEX(Sheet1!B4:I20,MATCH(YOUNG!E8,Sheet1!A4:A20,0),MATCH(YOUNG!K8,Sheet1!B3:I3,0)) ;

Notice: Undefined index: B in /var/www/cms_development/cms_gian/Classes/PHPExcel/Calculation/LookupRef.php on line 641

It shows this error ! . I cant find anyway to fix . Please help hehehe