Can I create a virtual directory in web.config?

Question

I have read that the applicationhost.config file sets the defaults and all directories below root inherit those settings.

I know its possible to change the defaultdirectory in a web.config, but I can't seem to do the same with a virtualdirectory.

Any pointers, help is appreciated.

Note: WEB.CONFIG file below DOES NOT work... just there to explain what I want to.

<?xml version="1.0" encoding="utf-8"?>

<configuration>

  <system.web>
    <customErrors mode="Off" />   
    <compilation debug="false" targetFramework="4.0" /> 
  </system.web>

  <system.webServer>
    <httpErrors errorMode="Detailed"  existingResponse="Auto"/>
    <asp scriptErrorSentToBrowser="true"/>

    <directoryBrowse enabled="false" />

    <defaultDocument>
      <files>
        <clear />
        <add value="Default.aspx" />
        <add value="default.html" />      
      </files>
    </defaultDocument>

    <httpProtocol>
      <customHeaders>
        <clear />
      </customHeaders>
    </httpProtocol>

  </system.webServer>


  <system.applicationHost>
    <sites>
      <site name="wed" id="1" serverAutoStart="true">

        <application path="/alpha-beta">
          <virtualDirectory path="/" physicalPath="\url.com\wwwroot\alpha\beta" />
        </application>
      </site>

      <applicationDefaults applicationPool="DefaultAppPool" />
      <virtualDirectoryDefaults allowSubDirConfig="true" />
    </sites>
  </system.applicationHost>
</configuration>