What's the best way to handle futures / commodity contracts in Netsuite?

We are a coffee roaster and buy green beans on the NYBOT. When you buy green beans on NYBOT you are first buying / committing to a quantity (pounds) and a price per pound (or whatever the UOM is). You are locked in to buy that quantity * price per so it's a liability from a Balance Sheet perspective. However, I then need to specify what country of origin that I want to buy and every Country has something called a "Differential"  - or a mark-up to the NYBOT price that reflects that country's premium for their coffees.

What I need help with is what type of transaction should I create in NetSuite when I purchase a futures contract on NYBOT for X pounds of green bean coffees PRIOR to knowing the specific origin (and it's corresponding differential) that we're going to buy.  I need NS to reflect my liability for the NYBOT contract and I'd normally think of a PO as it would create a payables liability. BUT, that only happens when I receive the PO. I haven't received anything yet...but I have locked in a liability. Then, once I now the final origin I'm buying and