You can have Best or you can have Cheapest, but you can't have both at the
same time.
Cheapest is a self-signed digital certificate that you can create your own
digital certificate. Rather than repeat the Help instructions here, I'll
simply say that to find out how, open Excel and use its Help to search for
the phrase
create digital signature
look for the returned topic "Create your own digital certificate'. It tells
how and the 'pitfalls'.
Also, go into the VB Editor and search for help on digital signature and it
will return a list of properties with example code that you can use in the
project to determine if a certificate is attached to it, who signed it, etc.
that you can use to verify that your signature is still attached to the
project and prevent code from running if someone has modified it (which will
result in the certificate removal).
Best is certificate with the public key stored in a trusted Root Certificate
server by someone like VeriSign and others. I think that the least expensive
of these that I've seen was offered by GoDaddy.com recently. You definitely
want to shop around some, as some sellers want major $$ for a certificate
through them.
Once you have a digital certificate, you attach it to a project from within
the VB Editor, choosing Tools | Digital Signature from the VB Editor menu
toolbar.
