MSBuild file which redefines a property

build.proj

<?xml version="1.0" encoding="utf-8"?>
<Project ToolsVersion="4.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
<Target Name="Build">
   <CreateProperty Value="firstValue">
     <Output
       TaskParameter="Value" PropertyName="LocalProp" />
   </CreateProperty>

   <Message Text="New value: $(LocalProp)" />

   <CreateProperty Value="secondValue">
     <Output
       TaskParameter="value" PropertyName="LocalProp" />
   </CreateProperty>

   <Message Text="New value: $(LocalProp)" />
</Target> 
</Project>