Change Order Approval Workflow

Summary

How to set up PO change order workflow based on amount increase/decrease?

Content

Client wanted to set up PO change order approval rules based on whether the PO was increased, which would go to approval. But if the PO was decreased, they want the change order to be auto approved. Is this possible and how would that rule be setup? 

 

So if the PO was increased, we want it to go to the approval group.
If the PO was decreased or any other change, we want it to auto approve.