How to create a log file for bapi return structure

Hi ppl,

I am using BAPI_PO_CHANGE to mark the delivery of POs as complete after many validations through a classic report now my concern is i have been asked to create a log file which details the errors in the POs which is in the bapi return structure.

I don't know how to do can any one help at the earliest.

Regards,

Bharathy.