Normally, you'd use Last() to check the value of a field from the last related record, but Last will not return a null value. It's defined to return the "last valid non-null related value".
IsEmpty ( GetNthRecord ( Jobs::WarrantyDate ; Count ( Jobs::JobID ) )
will be the last related jobs record's warrntyDate field is empty. If you need to reverse the logic, use Not in front of IsEmpty.
but you can also define a sort order in the relationship to make the most recent Job the first related record rather than the last. That would remove the need for the GetNthRecord function call. This could also produce a portal that lists the most recent jobs first and that is often a better order for portals that list some kind of "history" type list of entries.
Perfect!!!! Worked like a champ. I was indeed trying the Last() method. Thank you