Trying to add virutal directory with command line

I am able to add the directory but I cannot set the connect as option with the command line. Is there any way to do this?

We cannot use pass through authentication and need to set the user to connect as on the virtual directory. Normally when I am adding this manually I just click the connect as button, then select the Set radial button and enter the user name and password.

I cannot seem to find any options for appcmd.exe or any other command line tool that will allow me to set this.