Add a user defined field (UDF) to the Requirement entity. Then in the workflow editor, add this line:
Req_Fields("RQ_USER_01").Value = Req_Fields("RQ_ORDER_ID").Value
to the Req_AfterPost subroutine. The Order ID does not get established until after you post a new requirement, so it cannot be in the Req_New subroutine. You will need to add this new UDF to all requirement types that you want. Just be aware that if you move around requirements in the tree view, I believe the order id is fixed at the time you create the requirement, so it will not change with the move.