Why doesn't this code work on Flash Player 9?

programming flash
1

Hello!
I don’t really understand the differences between Flash player’s versions, so I don’t know why this code doesn’t work properly. Can anyone point me what’s wrong?


_root.centrey = 272;
_root.centrex = 510;
_root.onEnterFrame = function() {
    valeur_a = (_root._ymouse-_root.centrey)*0.5;
    valeur_b = valeur_b+valeur_a;
    valeur_b = valeur_b*0.8;
    _root.animation.block1._y = (valeur_b-_root.animation.block1._y)*0.05;
    _root.animation.block2._y = (valeur_b-_root.animation.block2._y)*0.1;
    _root.animation.block3._y = (valeur_b-_root.animation.block3._y)*0.15;
    _root.animation.block1._x = (_root._xmouse-_root.centrex)*0.02;
    _root.animation.block2._x = (_root._xmouse-_root.centrex)*0.04;
    _root.animation.block3._x = (_root._xmouse-_root.centrex)*0.06;
};

Thanks!