I have detail page on which I have created two fields - PageNumber__c and Book__c.
I have a requirement that if the pageNumber__C is populated with a value then the Book__c field should not be edited. How can I do this?
What I think - Can I make a validation rule, which would check if pageNumber__c is not null then if book__c isChanged() then throw an error. Is this approach possible. Any ideas?