Trouble with context when updating a validation rule

Question

I have an existing Validation rule on the Case that someone assisted me with earlier because it wasn't firing. Now that it's firing accurately, there is additional criteria I need to add to it but I'm getting tripped up on the context with the AND and OR's. Here is the existing rule:

AND( 
    ISPICKVAL(Status, "Request Approved"), 
    OR( 
       NOT(ISCHANGED(Status)), 
       NOT(OR(
              $Profile.Name = "HelpDesk User", 
              $Profile.Name = "System Administrator")
             )
          )
 )

This currently ensures that the only field that can be updated on the Case, when the current Status = Request Approved is the Status field and only users with Profile = System Admin OR HelpDesk User can make the updates. I need to also allow updating of another 2 fields: Current Approver and Approval Step Processed by the same 2 Profiles.

Answer 1

First, I recommend using Custom Permissions. This would make it easier to write.

AND(
  ISPICKVAL(PRIORVALUE(Status), "Request Approved"),
  NOT($Permission.Edit_Approved_Cases),
  OR(
    ISCHANGED(Status),
    ISCHANGED(Current_Approver__c),
    ISCHANGED(Approval_Step_Processed__c)
  )
)

Here, we check if the status was previously Request Approved, if the user does not have the Edit Approved Cases permission, and any of the "protected" fields have changed.

However...

Do. Not. Do. This. Period.

This type of validation rule is hostile to the user. They can now violate validation of any of the three fields, but the system UI cannot highlight a specific field, so they have to spend extra time finding which field(s) broke the rule. This is a Bad User Experience™.

Instead, use three validation rules. This also makes it easier to update in the future, as you can just copy-paste a formula and change as needed.

AND(
  ISPICKVAL(PRIORVALUE(Status), "Request Approved"),
  NOT($Permission.Edit_Approved_Cases),
  ISCHANGED(Status),
)

AND(
  ISPICKVAL(PRIORVALUE(Status), "Request Approved"),
  NOT($Permission.Edit_Approved_Cases),
  ISCHANGED(Current_Approver__c),
)

AND(
  ISPICKVAL(PRIORVALUE(Status), "Request Approved"),
  NOT($Permission.Edit_Approved_Cases),
  ISCHANGED(Approval_Step_Processed__c)
)

See how much easier this is to read? And, as a bonus, the correct field can be highlighted, making errors more obvious. Always prefer more validation rules than fewer.