Numeric fields and display values

Hi All,
I have a few numeric fields in my form. I want to display "null" in those fields when they do not contain a value in the db i.e. whenever the fields are left blank they should display "Null" in the form but will have a Null value in the db.
Any idea on how to do this?


Personally I'd have a WHEN-VALIDATE-ITEM trigger on the display items, and once the value had passed any validation I would update the database item accordingly (i.e. set db_field to TO_NUMBER(display_field) unless it's 'NULL' then set it to null). That way forms knows that the record has changed.