On a defect record type we have Resolution values defined.  When a user chooses a state, a set of Resolution values appear.  However the field automatically defaults to the first value in the list so it doesn't truly force the user to select from the list (unlike how other mandatory fields work in RTC).  The user can simply 'save' without selecting a value.  How can I set the field so that there is no default value and force the user to really pick from the list?