Custom PO approval workflow question

We have a custom PO approval workflow and currently at the last step of Approved state, the record is locked for everyone but a NetSuite admin.
Now, this has been raised as a major road-block from our product team because they frequently change the quantity or pricing of the items in the PO based on the feedback from the vendor they are working with.
So, if they change a quantity or the pricing then it ends up changing the total of the PO.

Now, our executives want to open up the edit option for users at the Approved state - but they need the approval workflow to start again ONLY if there was a change to the Total of the PO by plus or minus 10% of the original PO total. For e.g. if original Total was $100 and the new Total on the PO after PO was Approved is $111 or $89 then the executive needs to know about this and the approval workflow should start again. But if the new Total after the change is like $104 or $94 - less