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

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

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

b1_out = newImage('images/button1.png');
b1_over = newImage('images/buttonover1.png');