If you are using SQL Server 2008, you can use some of the new features that allow you to introduce triggers in DDL changes. You can then track based on the authenticated user who made the change.
I think these triggers are new to SQL 2008, but they may be available in 2005.
Having said that, ideally you should have a database schema under source control, using a tool like Visual Studio Database Professional. Then you will have a complete story of who does what.
Randy
Randy minder
source share