devenv Command Line - Adding Existing Project

[Narasimham]

Hi,

I was able to successfully create a new project using the devenv
command line arguments.
I did
devenv /command np
and then specified the name of the project and its location in the
dialog box.
After creating the project, I am trying to add an existing project to
the solution. As per MSDN, I should be able to use
devenv C:\TestBatchFile\TestApp17\TestApp17.sln /command
File.AddExistingProject
C:\TestBatchFile\TestApp17\CustomControls\CustomCo ntrols.csproj
where TestApp17.sln is my solution that already exists and
CustomControls.csproj is the existing project that i wish to add to the
solution. However, It is not working the way I expected it and is
simply opening the CustomControls.csproj in another Visual Studio
session. Can anyone help with this. I simply need to be able to add the
project to the solution.
When I do a File.AddExistingProject with the same parameters from
within the solution in the Command Window in Visual Studio, it
works.:-(
Regards,
Narasimham