BAPI_INTERNALORDER_CREATE plus profitability segment settlement

I am trying to create internal orders using BAPI_INTERNALORDER_CREATE, in the Settlement rules data I want to settle to profitability segment but I can't find away to do this. I can settle to other orders, cost centers and WBS elements but not PSG.

Are you guys aware of any way I cant do this. How can I derive profitability segment from PNL? is there other functions that will help do this?

Thank you very much

Omar