This is the pattern that I normally use for adding steps to the build report in TFS 2008. (See http://code.msdn.microsoft.com/buildwallboard/ for the full example that I usually use in my Team Build talks)
Basically, the magic is that there is a custom task provided for you in TFS2008 called "BuildStep". Here is the section where I generate and MSI installer and build the appropriate build steps in the report:
<Target Name="PackageBinaries">
<!-- create the build step -->
<BuildStep TeamFoundationServerUrl="$(TeamFoundationServerUrl)"
BuildUri="$(BuildUri)"
Message="Creating Installer"
Condition=" '$(IsDesktopBuild)' != 'true' " >
<Output TaskParameter="Id"
PropertyName="InstallerStepId" />
</BuildStep>
<!-- Create the MSI file using WiX -->
<MSBuild Projects="$(SolutionRoot)\SetupProject\wallboard.wixproj"
Properties="BinariesSource=$(OutDir);PublishDir=$(BinariesRoot);Configuration=%(ConfigurationToBuild.FlavourToBuild)" >
</MSBuild>
<!-- If we sucessfully built the installer, tell TFS -->
<BuildStep TeamFoundationServerUrl="$(TeamFoundationServerUrl)"
BuildUri="$(BuildUri)"
Id="$(InstallerStepId)"
Status="Succeeded"
Condition=" '$(IsDesktopBuild)' != 'true' " />
<!-- Note that the condition above means that we do not talk to TFS when doing a Desktop Build -->
<!-- If we error during this step, then tell TFS we failed-->
<OnError ExecuteTargets="MarkInstallerFailed" />
</Target>
<Target Name="MarkInstallerFailed">
<!-- Called by the PackageBinaries method if creating the installer fails -->
<BuildStep TeamFoundationServerUrl="$(TeamFoundationServerUrl)"
BuildUri="$(BuildUri)"
Id="$(InstallerStepId)"
Status="Failed"
Condition=" '$(IsDesktopBuild)' != 'true' " />
</Target>
So initially, I create the build step and save the Id of the step in a propery called InstallerStepId. After I have performed my task, I set the status of that step to Succeeded. If any errors occur during the step then I set the status of that step to Failed.
Good luck,
Martin.