Hi Metallo,

Of course, this is valid for my PC only, but when I send the file to another
PC, a message pops up saying that the certificate authority is unknown etc.
I was wondering: is that possible to send my certificate to the users
receiving the file so that they can benefit as well? In this way they would
not have to enable the macros every time.
If the answer is yes, how do I save the certificate in my PC and how do I
install it on other machines?

I don't think it's officially supported, but you can export and import digital
certificates using Control Panel Internet Options Content Certificates.
I haven't tested doing it for a selfcert ID.

Regards

Stephen Bullen
Microsoft MVP - Excel
www.BMSLtd.ie