function newImage(arg) {
rslt = new Image();
rslt.src = arg;
return rslt;
}

function bOver(image) {
document[image].src = eval(image +"_over.src");
}

function bOn(image) {
document[image].src = eval(image +"_on.src");
}

function bOut(image) {
document[image].src = eval(image +"_off.src");
}

b0_off = newImage('images/0_up.jpg');
b0_over = newImage('images/0_over.jpg');
b0_on = newImage('images/0_down.jpg');
b1_off = newImage('images/1_up.jpg');
b1_over = newImage('images/1_over.jpg');
b1_on = newImage('images/1_down.jpg');
b2_off = newImage('images/2_up.jpg');
b2_over = newImage('images/2_over.jpg');
b2_on = newImage('images/2_down.jpg');
b3_off = newImage('images/3_up.jpg');
b3_over = newImage('images/3_over.jpg');
b3_on = newImage('images/3_down.jpg');