Persist MSBuild properties into poperty group for project subtype

Hi,

I've been playing with the CSVSXProjectSubType sample from the MSDN samples gallery.

It works of course great, but I'd like to be able to persist build-related properties from the added project property tab.

In the sample, the extra properties end up in

<ProjectExtensions>
    <VisualStudio>
      <FlavorProperties>....

while I'd like to be more like

<PropertyGroup><MyExtraProperty>MyExtraPropertyValue</MyExtraProperty></PropertyGroup>

for usage is some custom target files.

The article

http://msdn.microsoft.com/en-us/library/bb491814%28v=vs.100%29.aspx

explains on how to achieve this with some code snippets. The code snippets are clear, but what is unclear to me is where I should put this code that is : how make it that is gets called.

I've looked to (amongst others) source code of the WiX project for inspiration, but I'm not creating a new kind of project here, merely adding some MSBuild properties and targets that will be using these properties.

Some additional pointers would be more than welcome.

(I'm developing for VS2010, if that would not clear).

Thanks,

Joris Spriet.