You can do a "self certification" which is suitable for testing purposes or
perhaps for limited internal distribution.

Check out my article here:

pubs.logicalexpressions.com/.../LPMArticle.asp

However, for professional deployment, you need to get a "code signing"
certificate or signature. There are different kinds of digital signatures /
certificates, and you need one of the "code signing" kind, as opposed to SSL
or others.

You need to purchase one from a certification authority, such as
verisign.com or thawte.com. There are many out there. I've used thawte.com
in the past.

This certification authority verifies your business identity and basically
certifies that you would never do something like create a virus and deploy
it.

Once they provide you with your digital signature, which is a small file
that you store on your hard drive, then you can "sign" your code  projects
with it, usually using Tools > Digital Signature > Sign As from a VBA Code
Editing window.

Then you want to be sure to save the file again (the template), and then
deploy.

When the user tries to access it, instead of getting the usual
Enable/Disable box in Medium security mode, they'll have the option of
trusting you as a source and accepting your signature on this template once
and for all, never to be bothered with the prompt again.