Purchasing cycle work flow

Dear All,

i would like to know how can i make the following Purchasing cycle work flow that implementing in my company

  1. Create PR User A

  2. Approve PR User B

  3. Send RFQ User C

  4. Fill the quotations on the system and compare request User C

  5. Release PO from approved PR User C

  6. Approve PO User D

  7. Receive the items User A

Which part are you struggling with - all seems possible to me.