Rewrite Rules with FileMapProvider

Hi,
I've installed the Url Rewrite Module 2.0 with the URL Rewrite Extensibility Samples (allowes us to use custom providers for the rewrite\redirect rules - in my case: external .txt file with the rules). I added the following lines to my web.config as shown in the tutorials at iis.net - http://learn.iis.net/page.aspx/803/using-custom-rewrite-providers-with-url-rewrite-module/ :

<rewrite>
<providers>
<provider name="FileMap" type="FileMapProvider, Microsoft.Web.Iis.Rewrite.Providers, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35">
<settings>
<add key="FilePath" value="{DOCUMENT_ROOT}\App_Data\redirectmappings.txt" />
<add key="IgnoreCase" value="1" />
<add key="Separator" value="," />
</settings>
</provider>
</providers>
<rules>
<rule name="FileMapProviderTest" stopProcessing="true">
<match url="(.*)" />
<conditions>
<add input="{FileMap:{R:1}}" pattern="(.+)" />
</conditions>
<action type="Redirect" url="{C:1}" />
</rule>
</rules>
</rewrite>

It works great, but I need to do is rewrite and not redirect. I have the following code:

<rule name="RewriteCustomDomainUser" stopProcessing="true">
<match url="^(.*)$" />
<conditions>
<add input="{HTTP_HOST}" pattern="^www.example-url-user1.com$" />
<add input="{REQUEST_FILENAME}" matchType="IsFile" negate="true" />
</conditions>
<action type="Rewrite" url="/user/user-one/{PATH_INFO}" appendQueryString="true" /> </rule>

This code rewrites the folder of a particular user for its own domain, it works fine, but get more and more users, it is difficult to add many rules in the web.config.

I added in my App_Data folder rewritemappings.txt file with this content:
www.example-url-user1.com, user-one
www.example-url-user2.com, user-anything
My question is if I can add these parameters in the rule RewriteCustomDomainUser with FileMapProvider.
Thank you very much!