How to add an expander in group in a Datagrid

Good morning,

I contact you cause I am working on a IHM in C# and I have to do some specific things.
I have a window which contains a data grid, check box and expander.
The IHM has to be like the picture below :



I followed some WPF tutorial and I tried to reproduce this IHM by using a CollectionView with a DataGrid.
I succeed to group the informations by Sections but the thing that I can't do is the expander inside each section.
I don't know how to proceed to do that and event it is possible.
Maybe someone have an idea.

Thank you in advance.