Doubt about BAPI_CONTRACT_CHANGE

Good morning Gurus.

I want to know how to connect an error message that is in the 't_return' to the corresponding item number to generate the ALV for the user.

CALL FUNCTION 'BAPI_CONTRACT_CHANGE'

             EXPORTING

               purchasingdocument = v_purchasingdocument

             TABLES

               item               = t_item

               itemx              = t_itemx

               item_text          = t_item_text

               return             = t_return.

For example:T_item has 10 itens and t_return have 2 errors How do I know which of the 10 items are in error.

Please see attach.

Thanks Gurus.