Using Environment Variables

I am trying to retrieve the user's login name this is the code I'm using:

Dim strUserName, strAddress As String

strUserName = Environment.GetEnvironmentVariable("username")
strAddress = "@chestnut.org"
UEmail = strUserName & strAddress

Now this works, but the output that UEmail displays is ASPNET@chestnut.org. I need the actual user's login name like rhinton@chestnut.org to show. I know that %USERNAME% will do this.