load testing user authentication

I have read something about vsts load testing: http://blogs.msdn.com/edglas/archive/2010/03/24/web-test-authoring-and-debugging-techniques-for-visual-studio-2010.aspx

Have one question, we need to perform a web load testing on the asp.net application. Instead of generating 100 virtual users, how can we load 100 users and password form users table programatically? the asp.net app uses form authentication.

Any advice will be appreciated.

Thanks!