Thanks, JP,

As it turns out, that is exactly the set of instructions I have been
trying to follow, but without success :(

Here's what I've done so far:

A.  In Windows 2000 I clicked on Start>Microsoft Office>Microsoft
Office Tools>Digital Certificate for VBA Projects.

B. In the "Create Digital Certificate" box that popped up I entereted
"My Digital Certificate" in the field labeled "Your certificate's
name:" and clicked OK.

C. I got a message saying "Successfully created...etc."

Then I tried to follow the instructions on that same web page you
suggested:

"1. On the Tools menu, click Options, and click the Security tab."

I take this to mean that I'm supposed to open the file I want to sign,
in this case the file containing my Excel worksheet.  Did I get that
right?  I had already reset the security level from high to medium, in
a previous attempt, so when the worksheet opened up, I got a choice of
disabling or enabling macros.  I chose "enable."

"2. Click Digital signatures."

Under "Signatures" the only only the that appears on the list is
Signer:Administrator Digital ID Issued By: Administrator Date:
3/22/2008.

"3. Click Add."

When I click "Add..." I get a message asking me if I want to save the
workbook.  I click yes."

"4. Select the certificate you want to add, and then click OK."

I get a list with two certificates, "My Digital Certificate" and
"Administrator."  I chose "Administrator because it had an expiration
date in 2106 as opposed to "My Digital Certificate" which has an
expiration date of 2014.

I clicked OK and then OK and then OK yet again.

I reset the Security Level to "High" and then clicked "Save."  I got a
warning that said "Saving will remove all digital signatures from the
workbook.  Do you want to continue?"

Well, no!  I went to all that trouble to add the digital signature.
Why would I want to remove it?

So I don't save the file, I just close it.

But then when I reopen it I'm faced with the "Macros are disabled
because the security level is set to High and a digitally signed
Trusted Certificate is not attached to the macros....etc."

So I'm right back to where I started.  And have been going round and
round in circles like this for days and days now.

So where have I gone wrong?

Will in Seattle
a.k.a. "Clueless