PO Extraction - Get Service Number !!

Hi all,

I working with 2lis_02_itm and 2lis_02_scl ; and i have to get the Service Number when the PO is a Service (like the material number when its PO of a Material).

Does anybody know how can i get it ? or do i have to enhacemente the Communication Estructure of 2lis_02_itm ?

Regards, i will asign points !!