Madhu,
My approach to this would be to use RedGate SQL Compare (I have no association other than as a satisfied customer-- ok they did give me a free pass to VSLive back in 2003, but that was after I was a satisfied customer) and make snapshots daily so that you can make comparisons and see what has changed.
Other approach look into using the C2 audit feature on SQL Server.
Last approach wait until you upgrade to SQL 2005 where you can enable DDL triggers to fire when someone makes schema changes.
David Lundell
Principal Consultant and Trainer
www.mutuallybeneficial.com