How to generate single purchase requisition from back-to-back sales order?

Summary:

Dear All,

How can I generate a single purchase requisition from a back to back sales order?

Scenario is:

We have 4 lines in the sales order, type is back to back. Currently system is creating 4 separate purchase requisitions.

Requirement:

Create a single requisition with 4 lines from the sales order.

Please help to achieve this.