You either have to merge to an output document and run some code to find all
the codes and apply the appropriate formatting, or do the same using VBA and
Word's MailMerge events. To do it purely using fields you need
a. to use the HTML formatting tags
b. to keep the data outside the database
c. to keep the link information in the database, e.g. have a field called
siglink containing "c:\\mysigs\\sig1.htm" etc
d. to use a nested field

{ INCLUDETEXT "{ MERGEFIELD siglink}" }

e. to accept that invalid tags may cause problems.

Peter Jamieson