Excel macro; "This CA Root certificate is not trusted because it is not in the Trusted Root Certification Authorities store"

Using Excel 2002 SP3 and am having fun with macros that I created. 
Every time I open a file using one of MY macros, I have to "Enable
Macros".  This, even after I created a "trusted source" locally on my
PC and selected it in the Tools/Macro/Security dialog box.

FWIW, Security Level is set to Medium.  Excel help describes how to
"Create your own digital certificate" by using SelfCert.exe.  But,
apparently, this doesn't satisfy Microsoft's requirements.  It appears
that the trusted source must be digitally signed.  So I google, and
find thawte.com, and there's several kinds of certs one can buy.  I
find CAcert.org, which offers free certs, but I am unsure if they are
the kind that satisfy MS Office (saw a mention by one of the
proponents that "most people rated inclusion into MS products as
unobtainable"), plus they require you to find a team of "assurers",
the closest of which is about 4 hours away.  Microsoft provides a list
of cert providers at
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnsecure/html/rootcertprog.asp.

Crud!  I just want to be able to open spreadsheets without having to
be bothered to "Enable Macros" everytime I open one that has *MY*
macros in it!  Can't I trust myself?!?!?

TIA, 
Dan