Dual header Listview

Question

I am trying to model an Excel-lookalike datapresenter using a Listview / Stackpanel / GridViewHeaderRowPresenter to get a dual-header ListView

This seems to work, but now I would like to show data from an ObservableCollection in code-behind C# using a GridViewRowPresenter.
This also works, but I can`t get it so that more lines of data will be presented, only 1.

Does anybody know how to do this?

My example source code (XAML and C#) is attached.

Thanx,
Reinier