Hi

I don't have much experience with Digital Signatures but it does get
rid of the dialog box but only on your Excel and not other people's.
They will still get the dialog box when they open your file.

Digital Signature are really only used to verify that you are a trusted
source but once it's opened first time by others they too can check the
box for 'Alway trust this source' and will never get it again.

Hope that explain a bit more

Tom