Hello Veselina,
I am working on a Sandbox. I do not have a ABAP developer key so I cannot modify anything anyways. I am just debugging and trying to learn about the Report.
I found out that BAPI_BILLINGDOC_CREATEMULTIPLE does the exact same thing. I have been able to create a External Billing Document successfully.
The problem I am facing now is Net Value of the Billing Document created is ZERO. I read on SAP SCN about the same problem being faced by others.
BAPI_BILLINGDOC_CREATEMULTIPLE
However this solution is not correct. I do not have a solution yet for the net value field. Please let me know if you have some information.
Thanks