Hello Andres,
Actually, the screenshots in my first post are a bit misleading as my structure has nodes Under like SAles Order -> Items.
To my current knowledge and looking at the other tutorial around XML Input, Excel cannot handle hierarchies (1 to many Relationship) and works with flat business object. (only a header).
If you need to create Items for a Sales order, like I did, you have to put the items as the objec. Thus repeating the Sales Order ID in each instance.
Thus all you elements should be in the root node.
In your example, you should try to build an object where CustomerActual is not an association, but where the elements are directly in the root node.
For more details on this, I would advise you to refer to the tutorial http://scn.sap.com/docs/DOC-52064#comment-569467 , and do not forget the comment section, very instructive . 
Thank you for your attention.
Best regards.
Jacque-Antoine Ollier