Approval Workflows - validation instead of just applying new value

Hello.

I want to create Approval Workflow for Unit Price change on Sales Order lines. I got this using standard ‘Revert the value of Unit Price field’ and ‘Apply the new values’ responses from Workflows Templates. Unfortunately - it is just applying values without validation.

After change Unit Prices approval requests is sending and previous unit price is reverting. But line amount is not updated - amount related to new (not approved) unit price remains.

I think if ‘Revert the value…’ (and later ‘Apply new value’) responses validate the field instead of just apply value the problem will be fixed.

How can I do this in the easiest way?