The BARCODE field produces only Postnet barcodes, and then only for valid US
Zip or Zip+4 numbers. If you need any other kind of barcode (UPC/EAN, Code
39, etc.) then you need to install the correct font and format your text
with it, or use a separate barcode generating program to produce a graphic
that you can import into Word.
For information and links to fonts and software, start at
http://www.adams1.com/pub/russadam/share.html or do a Google search.