Volume Level Adjustment (Discount) Functionality workaround in Procurement

Hello

Need help.

I was planning to use Volume Level Adjustment functionality in procurement. But since Volume Level adjustment is not supported in procurement, can any one please suggest workaround to achieve same results? The scenarios is:

1. Contract is signed with Vendor for specific quantity (say 10000) for a year

2. Contractual price is $10 for 5000 quantity

3. From 5001 quantity the price is $8 for balance quantities (Discount of $2)

4. The quantity could be achieved entering multiple PO's. System should accumulate the quantity of different PO's before next slap of $8 is applied.

I have gone through the white paper of Catalog pricing & Discount in procurement. It does not work if Procurement Advanced Pricing is activated hence was trying to achieve the same using volume level adjustment. But that too is not supported.