Discount amount - Fixed amount at vendor bill header rather than percent

Since NetSuite will not allow you to enter a flat discount amount (you must use payment terms) when entering a vendor bill, what is your recommended solution for someone who only has expenses on the vendor bills. No items, no purchase orders, just regular old expenses. Besides reducing the amount of the bill total and netting out the discount line item, I don't have a better way. And no, I don't want to change the amount of the discount taken when 'paying bill'. I also do not want to create 72 different possibilities of discount percents just in case I