I forgot to say that i'm also a perfect newbie in the C world, so the interrupts are quite obscure for me, but as you said, it seems a bit complicated for such a little added value 
And even if i would certainly learn loads of interesting things by doing that kind of stupid thing, I really don't have enough C background to do this anyway.
But, just to go back to the main problem, I guess you have no idea or not enough informations to know why it's not working.? 