Tfsbuild MakDir to the output directory

Question

I have a TFSBuild.proj which I want to edit slightly at the end - I want to make a bunch of directories and dump a few things in them. The problem I'm having is that the straightforward method dumps the new folder into the specified drop folder for all builds rather than the folder created for the current build.

For example I had something like this:

<PropertyGroup>
     <DropLocation>\\myloc\builddir</DropLocation>
</PropertyGroup>

<Target Name="AfterCompile">
    <MakeDir Directories=$(DropLocation)\testdir />
</Target>

Obviously this creates a directory in myloc\builddir rather than in the newly created folder containing the build. I then tried:

<Target Name="AfterCompile">
    <MakeDir Directories=$(OutDir)\testdir />
</Target>

Which I hoped would slot the directory into my output directory, but still no dice. Any help? I'm sure I'm just doing something totally dumb somewhere along the line, but I'm still flummoxed.