[Ben]

mc.onRollOver = mc_over;
 
function mc_over() {
this.onEnterFrame = something;
delete this.onRollOver;
}
 
var b = bounds_mc.getbounds (_root);
 
function something() {
if (_xmouse<b.xMin  || _xmouse>b.bMax || _ymouse<b.yMin || _ymouse>b.yMax {
this.onRollOver = mc_over;
delete this.onEnterFrame;
}
} 

edit: Im always too Slow !!!!