Use of Procurement caegory on a purchase requisitio

Hi all,
I need some advices to do this scenario: We need to create a purchase requisition in AX 2012 where we must

  • There is a need to buy some flyers ( Procurement Category: MRKT)
  • Purchase requisition must be created with flyers then go to approval flow. Once the PR is approved , an item shouldbe created in the master file; the PR should be modified to replace the procurement category with that item. We need to keep a trace or link between that item and the procurement category. After that a PO should be created . How can I setup that scenario