Custom Order Export - Need Help

[Caloby]

We use several vendors and each one requires a unique order file. I was attempting to create a custom order export for each vendor, but there are several fields missing in the drop down box for Build Export Sets.

Need to add the following:
manufacturer_id
itemname
numitems
unitcost


The last 3 above show up if the Include Order Items box is checked, however I need the option to select them in the Build Export Sets so I can assign the order and use an alias.

Is this possible? Am I missing a step somewhere?

Thanks...