Approver allowed to change FI document fields before approving the document

Hello,

We come across a scenario, where we found that WF approver for a document can go to change document and allowed to change the sensitive fields for eg: document amount. Check where person who parked is not allowed to post is working, but the check doesn't work if before approval, approver happen to change the document and than after saving approves it. This is SOX issue.

Does anyone come across the same issue and if there is any suggestion so we can add control.

Thanks,

MS..