Activate Rebates for Old Sales orders created

Hi SAP Gurus,

How to activate rebate agreement or rebate condition records to old sales orders which has been created at past ?

let me take an example and explain:

1. Total sales cycle is created (Sales Order, Delivery & Billing with Accounting document) is created on 06.06.2014 and rebate agreement is created on 26.06.2014.

Now my client is asking to link the rebate agreement which is created on 26.06.2014 to the Sales Cycle which is created and completed on 06.06.2014.

Balajia