How do you route an invoice for reapproval after it's already been approved?

Hello -

First I'll explain why and how we've been handling this in the past.  For non-PO invoices we ask the that the approver enter the accounting at the time of approval.  If they forget to add the accouting or enter the wrong accounting we need to send out the invoice for approval again so that it can be corrected.  Currently to change the invoice to the "needs reapproval" state we make a change to the invoice amount and then change it back right away.  This has been causing some payment problems because sometimes the payment schedule amount doesn't match to the invoice