function CSDateChooser_SetValueToHidden(inputID, hiddenID, NullValueDisplay)
{
    var input = $get(inputID);
    var hidden = $get(hiddenID);
    if (NullValueDisplay != null) {
        if (input.value == NullValueDisplay)
            hidden.value = null;
        else
            hidden.value = input.value;
    }
    else
        hidden.value = input.value;
    alert(hidden.value);
}

function CSDateChooser_ShowHideNullValue(inputID, spanID) {
    var input = $get(inputID);
    var spanID = $get(spanID);
    if ((spanID.innerText != null) && (spanID.innerText != "")) {
        if ((input.value == null) || (input.value == "") || (input.value == "__/__/____"))
            spanID.style.visibility = "visible";
        else
            spanID.style.visibility = "hidden";
    }
    else
        spanID.style.visibility = "hidden";
}