Hi Thierry,
Frank Dauche, who used to actively post in this forum, found a way to do this using the technique you describe. It was a little tricky to get the correct window handle, but so long as you have some managed code, you can access the properties for your window. I asked him to post his solution, but he got hired at Microsoft and has been busy ever since. I'll ping him again and see what he is doing. Bottom line: it's doable.
Cheers!
Patrick Halstead
Project Manager at Qdabra