Digitally Signing Excel/Word Macros

Hello, we have some custom macros that we've written and added to Word and
Excel to facilitate connectivity with our document management system. The
problem is that users are prompted to enable or disable macros every time
they open Word or Excel. I know that I can make my own certificate and
manually distribute it to every computer or buy a trusted certificate from
Verisign or others but my question is, if I did buy a cert from Verisign or
others, where/how to I go about using it on my network?

Do I have to installl the certificate authority to run on a Domain
controller or member server? Can anyone give me the scoop on if this is the
way to go or is there another way?

Any suggestions would be appreciated.

Thanks

Jim