Is it possible to prevent project managers to change effective cost rate?

Summary:

How to prevent project managers to change effective cost rate in the financial plan

Content (required):

We want to prevent project managers to change the effective rate for labor reasource assignment, in order to use alway the standard rate taken from planning rates. Is it possible?

Version (include the version you are using, if applicable):

23B

Code Snippet (add any code snippets that support your topic, if applicable):