Workflow Process- PO Cancellation/Rejection

Dear Experts,

We are configuring Workflow Email generation while cancelling a Purchase Order in SAP through ME29N. Can anyone please guide me on how to configure release strategy for PO cancellation? Currently we are on SAP version 4.7. I have configured the workflow for PO approval, however unable to find the way for configuring PO reject in SAP MM.

PO reject/cancellation is also considered as a change process in workflow. In this case how do we go about the workflow set up? Any inputs for this?

Thanks for your help in advance.