No, it isn't really possible to prevent it completely if you're using
Word at all. The best you can do is make it more difficult.

You can write macros to intercept the Save and Save As commands
(http://www.word.mvps.org/FAQs/MacrosVBA/InterceptSavePrint.htm). The
macros can be empty so the commands appear to do nothing, or they can
display a message like "Don't do that". The problem is that if the
user's security level is High the macros won't run at all; if the
level is Medium, the user gets to decide whether to enable or disable
the macros. So you can't count on this working for everyone --
especially users who know a bit about Word.

I suggest instead a bold red statement across the top or bottom of the
form warning of dire consequences if they don't use the form from the
website. For example, "Claims not submitted through the web form may
not be paid."

--
Regards,
Jay Freedman
Microsoft Word MVP        FAQ: http://word.mvps.org
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