Validate Goal Category based on Employee's Grade in Goal Management

Summary:

We have a requirement to validate the goal category based on employee's grade, certain grades can only select some category values.

Example: Only employee in grade 15 and above can select value "Company", if selected by other grade then it should throw an error.

We tried using VB validation on My Team goal page but there is no grade field available, we tried with role field as well but even it is not working as expected.

Goal setting as process is being done by immediate Line manager not by employee, hence role is also not working.

Any idea how this can be achieved.