Dynamics Word template with multi-level relationships

Hi,

I am trying to create a Word template, in this case for the Account entity. I want to create a Word template that includes the Orders of an Account, and for Each Order all the Order Details.

Out-of-the-box, the Word templates only allows one level down to choose from, but this blogpost mentions that it should be possible to create custom XML fetch queries to get more data into the Wordt template. However, I am not sure where to put the custom C# code that is mentioned in the post; does that go somewhere inside the template itself, or is that custom code that has to be registered somehow as a plugin?

Thanks,
Koen