asp.net webconfig, how to read from a config source file for default documents

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ASP.NET

I'm working with a Web.config file and running on iis 7 using asp.net 3.5.
I was wondering if there is a way to keep a list of default documents in a separate file.

for instance instead of this:

<defaultDocument>
     <files>

       <remove value="Default.htm" />
       <add value="portalmain.aspx" />

     </files>
</defaultDocument>

We read the values from another config file:

<defaultDocument>
     <files configSource="WebDefaultDocuments.config"/>
</defaultDocument>

Thanks