Your question may be simpler but an answer probably is not (as usual!)
To do this using a MailMerge approach, you could start as follows.
Suppose you make a Word tempalte (or document - I do not think it makes much
difference in this case) that uses your Contact's folder as its Mail Merge
Data Source. Save the template/document, and re-open it, or create a new
document based on the template. At that point you will I think be asked
(twice) to select your contacts folder. That's the real problem here, as we
shall see
Let's suppose you now try to restrict your data source to the one contact
you want to use. You will need to have criteria that uniquely identify the
contact - e.g. Firstname, lastname may or may not be enough.
Open the Mail Merge Recipients dialog box, clcik the drop-down at the top of
one of the columns, and seelct Advanced to view the Query Options dialog.
You can then specify the conditions needed to select that one record. When
you get back into the Mail merge Recipients Dialog box, only one row should
be displayed. Incidentally, you could just "clear" all the entries, and
select the one you want, but then you would be relying on Word's internal,
undocumented mechanism for identifying which records you have selected and I
suspect that is best avoided.
Now close the recipients dialog box. Show the preview data including the
address that you want to see updated. Save the template. Experimentally
change the address data for the contact. When you re-open the Word template,
and select the correct contacts folder, the new data from the contact should
be displayed. However, you have to know which contacts folder to open. If
you get the wrong one, Word won't find the record you wanted.
There is another way you can go about doing this, which is to use Access to
link to a Contacts folder, then use that linked Access table as your data
source. It seems to work quite well to me and avoids some of the problems
mentioned above. At the moment I can only tell you how it works if you have
Access, but a programmatic solution may also be feasible.
Peter Jamieson