Using Product Fiscal Classification in iProc on non-catalog requisition as eBTax determining factor

We would like to create a category-like classification on our non-catalog requisitions where a user can, in iProc, indicate what kind of requisition it is. For instance a service, a training course, or food. The field "Product Fiscal Classification" is available in iProc at the checkout, which may be useful in achieving this goal. However, metalink notes on using this field when Inventory is installed only described how this field can be used when associated to an item. Is it possible to use this field when entering a non-catalog requisition? If so, how do we set up the LOV to