Hello, Salesforce Professionals 

I need to create a validation rule that will prevent creating records with the same proprietary_number__c field on billing__c object.

I wrote this formula: 

and(
proprietary_number__c = VLOOKUP
($ObjectType.billing__c.Fields.proprietary_number__c , $ObjectType.billing__c.Fields.Name , proprietary_number__c ),

not(
Id=VLOOKUP
($ObjectType.billing__c.Fields.Id , $ObjectType.billing__c.Fields.Name , proprietary_number__c )))   

But it doesn't work. I still can create a record with a duplicate proprietary_number__c  field. 

Please, help me. I can't understand what I am missing in this formula. 

Thank you in advance.