Integration with Word XP

I am running Office XP, and want to create a Word letter template which will prompt users to select the addressee from a drop-down list from Outlook Contacts. I hope to do this using Word's toolbar command InsertAddress.
My problem is that the contacts are listed alphabetically by first name, when I want them listed alphabetically by last name.
In Outlook Options, have changed Contact Options appropriately, but this hasn't helped.  I note that this option is stated to apply only to new contacts.  Is there a way of changing existing contacts so they will display correctly in Word's InsertAddress command?  (NB I have posted a similar question in the Word forum).