How to monitor a single db of an instance in SQL Server
You can accomplish this with the SQL Server Profiler.

http://msdn.microsoft.com/en-us/library/ms181091.aspx

First you will want to create a trace.

http://msdn.microsoft.com/en-us/library/ms175047.aspx

Then you will want to specify the events you want to track.

http://msdn.microsoft.com/en-us/library/ms188674.aspx

Then setup a filter for the database name.

http://msdn.microsoft.com/en-us/library/ms175520.aspx