Purchasing Unit of Measure

We are interfacing requisitions from another ERP package (INFOR) into Oracle Purchasing. INFOR is able to define a purchasing unit of measure and we have the requirement that this be done in Oracle also. I see that I can do this if using blanket POs, but my customer does not use blankets. An example would be an inventory item with the primary Unit of Measure of Foot. The purchasing unit of measure is supposed to be Roll. I see that I can change to Roll on the PO, but I don't see a way to automatically make this happen short