How to update requisitions with approval status and data

Summary:

Please advise how to update the requisitions created in Oracle Self Service Procurement with the approval status and data processed in the external system.

Content (required):

We are considering to build requisition approval process in the external system due to the complex approval rules and get back the approval status to the requisitions created in Oracle.

Our solution is as follows.

1. Create a requisition and submit for approval in Oracle Self Service Procurement. At this moment, approver is set as a "dummy user" so that the requisition waiting for approval by the dummy user cannot be updated nor withdrawn.