Can Vendor Discount Schedules be based on Total Order instead of Quantity?

Hi All,

Does anyone know how to set up a vendor discount based on order total.  My vendors give me discounts based on how much I spend per order. 

For example, vendor A gives me 10% off of $1000.  Of course, we always order $1000 at a time, so I created a schedule that says that any quantity over 1 will have a 10% discount. 

But now, I have vendor B.  Vendor B gives me 5% at $500, and 15% at $1,000.   So I can use the method above, except that Vendor B also drop ships small orders for us.  Those do not qualify for the discount, so I want to create a quantity discount schedule based on order total instead of quantity of items.