I need to create a validation rule that fires where when either "Complete" or "Closed" is chosen from a picklist, another picklist becomes a required field. I have tried multiple options, but have not had luck yet. So far this is what I have tried:
AND ( ISPICKVAL(Status__c, "Complete" || ISPICKVAL (Status__c, "Closed"), NOT(ISCHANGED(Root_Cause__c)) )
Both Root_Cause__c and Status__c are picklists.
I am currently getting a FIELD_CUSTOM_VALIDATION_EXCEPTION error on the page. Anyone have any ideas?