<Project ToolsVersion="4.0"
         DefaultTargets="Deploy"
         xmlns="http://schemas.microsoft.com/developer/msbuild/2003">

    <UsingTask TaskName="TransformXml"
               AssemblyFile="$(MSBuildExtensionsPath)\Microsoft\VisualStudio\v10.0\Web\Microsoft.Web.Publishing.Tasks.dll"/>

    <PropertyGroup>
        <ProjectPath>C:\Path to Project\Here</ProjectPath>
        <DeployPath>C:\Path to Deploy\There</DeployPath>
        <TransformInputFile>$(ProjectPath)\Web.config</TransformInputFile>
        <TransformFile>$(ProjectPath)\Web.$(Configuration).config</TransformFile>
        <TransformOutputFile>$(DeployPath)\Web.config</TransformOutputFile>
        <StackTraceEnabled>False</StackTraceEnabled>
    </PropertyGroup>


    <Target Name="Transform">
        <TransformXml Source="$(TransformInputFile)"
                      Transform="$(TransformFile)"
                      Destination="$(TransformOutputFile)"
                      Condition="some condition here"
                      StackTrace="$(StackTraceEnabled)" />
    </Target>
</Project>