Hi Daniel,
Thanks for your explanation. I see two options to proceed.
Option 1: Create a Generic Extractor based on table CABN
Enhance the DataSource with an additional field to store the external value of field ATINN. In the coding you have to use Function Module CONVERSION_EXIT_ATINN_OUTPUT.
Option 2: Create a Generic DataSource based on a Function Module
This is a more complicated option but certainly possible. You will have to extract from table CABN. Also here you will have to define field which stores the external value of field ATINN.
Please refer to e.g. document SAP BI Generic Extraction Using a Function Module for a detailed instruction how to create such a Function Module extractor.
Best regards,
Sander