I use Novell Teaming 2.1. Is it posible to limit user access to individual form elements?

For example, I have a form Invoice Registration. That form has the elements Supplier, Invoiced Amount, Due Date, Aproved by and some more.

How can I achieve that nobody but the user Joe Blow to be able to modify the element Due Date

and

nobody but the user Mary White to be able to modify the element Aproved by.