Supplier Notification should not be sent when the value of PO is decreased

We have customized the CREATEPO workflow to be kicked off at the end of requisition approval workflow and create the approved PO automatically.

 

Subsequently when the amount of Requisition is increased or decreased via change request,  the amount is reflected also in the PO(no explicit approval on PO required).

 

The requirement is if there is a change request in the Requisition (when we are varying down the value) , the PO email (via PO Output for communication) should not be triggered to the vendors.

 

Is there a way to achieve this?

 

Regards,

Div