I need to add a validation rule for if a certain profile is assigned to a Secondary AM field that it won't save. I don't want this profile to be able to be assigned to this field and so need an error message to pop up so people know not to assign certain users.

I need to add a validation rule for if a certain profile is assigned to a Secondary AM field that it won't save. I don't want this profile to be able to be assigned to this field and so need an error message to pop up so people know not to assign certain users.