Disable PO Approval's rules

Hi,

How can I make that the settings of Oracle Purchasing does not automatically approves a purchase order even if the unit price and the quantity wiil be reduced after approval of the purchase order?

I need that any change in the purchase order (even for less value) it needs to be referred and reapproved by an hierarchy's approver.

I already verified the setup walkthrough of workflow builder that the attribute's value from the unit price tolerance is equal to zero.

Even after this I didn't get the solution yet.

Oracle EBS version 11.5.10

Best regards.

Gelmini