Create service PO from BAPI_PO_CREATE1 w.r.t a service PR

Hi experts,

we have a requirement to create a service PO from Service PR through BAPI BAPI_PO_CREATE1 , but when i am trying to create it is giving error 'Maintain Service or LImit' . i want to know from where i can get the service line item from PR which i can pass in POSERVICE parameter of the BAPI. I mean i want data from ESLL table to populate in the service PO importing parameter but don't know how to get ESLL data from PR detail.

Thanks in Advance !

Regards,

Kapil.