I am working on a telephone # class that copies the behavior of the Outlook - Contacts phone number (textbox for the # and dropdown list for the phone # type). The class uses a view, created on the fly, of the phone # table. The table stores the # along with the parent table name and the PK of the record in the parent table.
Since there are several types of phone numbers, I don't expect the users will be satisfied with having only one textbox to show all the numbers. I expect this class will be used several times on a form, showing different type #'s as the default. I want the classes to be aware of each other so that if the home # is changed on txt1 on page 1 that txt2 on page 2 reflects the change (but before the save or cancel updates or reverts the changes).
Is this an appropriate use for an observer class? I assume the class would have to be on the form, but could it be part of the phone class (so that I wouldn't have to have another class)? What is the best way to implement such a class?

TIA
John