for (i=0; i<arrChecks.length; i++)
{
    var attribute = arrChecks[i].getAttribute("xid")
    if (attribute == elementName)
    {
        // if the current state is checked, unchecked and vice-versa
        if (arrChecks[i].checked)
        {
            arrChecks[i].checked = false;
        } else {
            arrChecks[i].checked = true;
        }

    } else {
        arrChecks[i].checked = false;
    }
}