VBScript Error handling

I am writing a site using ASP 3.0 pages and VBScript. I am connecting to a SQL Server 2k database and running on a Windows 2k IIS server.
I am using Windows security to log people in but need to know how to capture if a user hasn’t got permission to the database and show an error page telling them they do not have permissions. I need to do this in the VBScript. How do I go about this?