Rebate use as a discount for next order

Hi,

This is a JDE E1 scenario.

The Scenario given below -

Ex. -

1. whenever customer reaches a threshold of 1000 EA (Unit price = 20 $) of an order. customer will get 500 $.

2. Here company doesn't want to give that 500 $ as a credit amount to the customer.

3. Condition is that 500 $ will be used as a discount when customer order minimum 200 EA in next order.

How can i automate this process ? I understand that 1st step i can achieve by using rebate. But i am not sure how can i achieve the step 3.

Thanks,

Vishal