BAPI - Custom fields

Hi Guys:

I would like to use the BAPI of Sales order <b>BAPI_SALESORDER_CREATEFROMDAT2</b> and have small doubt in my mind. Already some Custom fields are added in the Sales Order item Level Additional <b>TabA and TabB</b>. How can i simulate the Custom fields to above mentioned BAPI. Is Userexit will solve the purpose of mine?

Suggestions are welcome.

Thanks in Advance

Regards

Suresh Babu Karanam