Web.config Transform variables

Is it possible to include variables in a web.config transform file? For each environment, I have basically the same transform, just with different values. For example, for the development environment, I'd have...

<?xml version="1.0"?>
<configuration xmlns:xdt="http://schemas.microsoft.com/XML-Document-Transform">
    <appSettings>
        <add key="serverName" value="server1" xdt:Transform="Replace" xdt:Locator="Match(key)" />
        <add key="serverPath" value="\\server1" xdt:Transform="Replace" xdt:Locator="Match(key)" />
    </appSettings>
</configuration>

And for the QA environment, I'd have...

<?xml version="1.0"?>
<configuration xmlns:xdt="http://schemas.microsoft.com/XML-Document-Transform">
    <appSettings>
        <add key="serverName" value="server2" xdt:Transform="Replace" xdt:Locator="Match(key)" />
        <add key="serverPath" value="\\server2" xdt:Transform="Replace" xdt:Locator="Match(key)" />
    </appSettings>
</configuration>

The only difference is the value for server1 vs server2. This is a simple example, and in reality, I use the server value multiple times in the transform. Is there any way to declare a variable in the transform file to be used multiple times? Something like...

<?xml version="1.0"?>
<configuration xmlns:xdt="http://schemas.microsoft.com/XML-Document-Transform">
    <property name="server" value="server2" />
    <appSettings>
        <add key="serverName" value="${server}" xdt:Transform="Replace" xdt:Locator="Match(key)" />
        <add key="serverPath" value="\\${server}" xdt:Transform="Replace" xdt:Locator="Match(key)" />
    </appSettings>
</configuration>