function openWindow(sUrl,sWidth,sHeight) {

    leftVal = (screen.width - sWidth) / 2;
    topVal = (screen.height - sHeight) / 2;

    newWindow = window.open(sUrl, 'VPOP', 'resizable=yes,scrollbars=yes,width=' + sWidth + ',height=' + sHeight + ',left=' + leftVal + ',top=' + topVal);
}