Digital ID from one account of 3 in Outlook 2003 (SP2)

[Mark]

Hi there,

I am just looking to try and add a Digital ID to one account of 3
accounts I manage using outlook.

But when I set tools/options/security/Add digital Signiture to
outgoing messages it errors on the accounts I do not have or want a
digital ID for.

Is there anyway I can setup outlook, so that it only adds the digital
signature (and encrypts) messages from one account associated to
outlook?

Many thanks

Mark