How to link document status to another document

We’re nearing the end of setting up a construction company warehouse. We’ve had to tailor the Material Request concept to suit the company workflow. But there is still a missing part. The process is:

  1. Construction sites request for Materials from HQ to encourage re-usage and improve oversight
  2. HQ Procures all items to their Main Warehouse
  3. Then Main Warehouse Transfers the materials to the requesting Site

Our problem is that we need to know the status of the request all the way from Request to Delivery on Site but the Stock Entry (Transfer) cannot be linked to the Material Request by default. We need to link the Stock Transfer Material Request status, or something of the sort so one can track the complete status of the Material Request.

The default Material Request does this up to purchase. Knowing how ERPNext default setup does this can provide clues.

Please help us find a solution to this problem.