Lock personnel numbers from being edited

Hello

I am in the middle of a system migration which is being done in phases; some personnel numbers have been moved and some remain in the legacy system.  Is there a way to lock the already migrated ones from being edited through PA30, PA40 in SAP?  The HR staff keep forgetting to use the new SAP environment so it is important to stop them from making changes in the old SAP.

Thanks.

PC