I used this good article to make this : http://www.ethicalhacker.net/content/view/207/24/
To resume you copy the orignal dll in OOo program folder, you rename it (user33 for example) you create another dll named user32 in which you add some code in some functions and redirect all the others. And finally you modify the manifest file to tell the application to load the dll in the folder not the one from system32.
I've made several tries with other applications it works fine, with OOo it doesn't
So i tried with other dlls, the only which work is ole32 ...
So if anybody have a clue for me it would be great.
Thanks in advance.