IIS Express to use

Profile Location:

"%userprofile%\My Documents\IISExpress\config\applicationhost.config"

Site Configuration section:

<site name="MyTopLevelAndChildWebAppsInOneSite" id="123" >
    <application path="/" applicationPool="Clr4IntegratedAppPool">
        <virtualDirectory path="/" physicalPath="C:\Users\me\Source\TopLevelWebApp" />
    </application>
    <application path="/Child" applicationPool="Clr4IntegratedAppPool">
        <virtualDirectory path="/" physicalPath="C:\Users\me\Source\ChildWebApp" />
    </application>
    <bindings>
        <binding protocol="http" bindingInformation="*:51234:192.168.0.10" />
    </bindings>
</site>

Start Site (32):

start "Woo!" "C:\Program Files (x86)\IIS Express\iisexpress.exe" /siteid:123

Start Site (64):

start "Woo!" "C:\Program Files\IIS Express\iisexpress.exe" /siteid:123

Note that if a local or external network access, open firewall ports