SD_SALESDOCUMENT_CREATE : Billing Type field

Hi Guyz..

I'm trying to create a Debit Memo using this Function Module.

I have to populate the Billing Type at the item level. You can see this field on the item level "Billing Plan" tab in the table control if you scroll all the way to the right.

But I can't find it in the SALES_ITEMS_IN table structure.

Any ideas here as to how to populate this field?

Thanks!