BAPI_SALESORDER_CREATEFROMDAT2

I am using a program that calls the function module BAPI_SALESORDER_CREATEFROMDAT2 to create sales orders. The function module works fine except for the situation where I am trying to create a direct sales order. The function module errors out and says that I need to enter a purchasing group. I have looked at all of the fields you can pass the function module and have been unable to find anything that looks like it might be a purcahsing group. Is there a way to do this?

thanks.