I got this by going to the search feature in the start menu. It took me to a
Microsoft bulletin:

You can also use a digital signature that is created with Microsoft
Certificate Server. Certificate Server is included with Microsoft Windows NT
4.0 Option Pack, with Microsoft Windows 2000 Server, and with Microsoft
Windows Server 2003.

For more information, go to the Help and Support search feature through the
Start menu.

"Carlos" wrote:

Hello everyone,

Do you know how to attach a digital signature to a workbook. I designed an
Add-In that validates the workbook, and I want the last macro to digitally
sign it if the validation process is successful. I've seen the help files but
they only contain information about how to do it in Word and the 'signature'
and 'signatureset' classes are not part of Excel's library.

Thanks in advance,

--
Carlos