function PreLoad() {
ImageOverTop = "url(button_blank_blue_top.gif)";
ImageOutTop = "url(button_blank_white_top.gif)";
ImageOverMiddle = "url(button_blank_blue_middle.gif)";
ImageOutMiddle = "url(button_blank_white_middle.gif)";
ImageOverBottom = "url(button_blank_blue_bottom.gif)";
ImageOutBottom = "url(button_blank_white_bottom.gif)";
}

function overTop(td_id) {
document.getElementById(td_id).style.backgroundImage = ImageOverTop;
}

function outTop(td_id) {
document.getElementById(td_id).style.backgroundImage = ImageOutTop;
}

function overMiddle(td_id) {
document.getElementById(td_id).style.backgroundImage = ImageOverMiddle;
}

function outMiddle(td_id) {
document.getElementById(td_id).style.backgroundImage = ImageOutMiddle;
}

function overBottom(td_id) {
document.getElementById(td_id).style.backgroundImage = ImageOverBottom;
}

function outBottom(td_id) {
document.getElementById(td_id).style.backgroundImage = ImageOutBottom;
}