In my Web Application I have 3 different build configuriations:
- Debug
- Release
- Demo
My Web Application will be copied into three different folders depending on these three configurations:

In my output path I get the following 3 folders: C:\Projects\MyWebApp\

Now I can call these 3 folders via the IIS Express, when I use subdomains. I have added these lines to my applicationhost.config:

Now I am able to access my 3 different folders via 3 different subdomains in the browser:
My Problem:
How can I teach Visual Studio 2013 to use the url of the current choosen configuration? I tried the following:

Unfortunately Visual Studio is not able to process environment variables in this field.