Approval workflow for when an unmatched invoice line amount exceeds 10% of invoice amount

We need to create an approval workflow where invoice is matched with PO but it has one line which is not matched with PO. If the invoice line amount is greater than 10% total invoice amount then it should have different hierarchy.

Currently we have hierarchy for the same based on 500 QAR amount but I want to setup based on percentage. How can we achieve this based on percentage?