Thanks all for the helpful advice. None of them worked - and then
they did. Very puzzling. doubtless this will take longer to get
finally resolved. Anyway, this currently seems to work.

tell application "QuarkXPress�"
   activate
     tell document 1
       repeat with i from 1 to  (get count pages)
         tell page i
         show
           try
             set (font of every character of every text box whose ¬
             font is "AGaramond" and (it is in "1234567890")) to "AGaramondExp"
           end try
         end tell
       end repeat
     display dialog "Script completed successfully!"
   end tell
end tell

Using
             set (font of every character of every text box whose ¬
            (it is in "1234567890") and font is "AGaramond" ) to "AGaramondExp"

Also seems to work. I don't know if there is any speed difference
between the two.
--
_________________
Dr Digby L. James
Quinta Press
http://www.quintapress.com
Meadow View
Weston Rhyn
Oswestry
Shropshire
England
SY10 7RN
Phone (44)(0)1691 778659
Mobile (44) (0)7970 678144
Fax (44)(0)1691 777638
_________________