The Advanced Security for Outlook from http://www.mapilab.com/outlook/security/ is free Outlook add-in that allows end-user to take control over Outlook security alerts.

The Outlook model doesn't provide access to the Label property, but it can be retrieved/changed via CDO 1.21.
Requires Outlook 2002 or later. Tested with Outlook 2003 only.
Based on http://www.outlookcode.com/codedetail.aspx?id=139

Code is based on http://msdn2.microsoft.com/en-us/library/Aa155615