Restrict editing a metadata field while in a workflow

Is there a way to restrict the editing of a metadata field on an object until that object has reached the end/final status of a workflow?

I have a metadata field called "Contract Status". It is set automatically as part of the contract workflow to "Draft", until at the end of the workflow it will be set automatically to "Active". Right now, anyone with access to the contract object can modify that field at any time. I would like to restrict access to edit the field until the end of the workflow, where the status is "Contract Awarded".

Does anyone have any suggestions or tips on how to do this?