var postponedCallbackValue = null;
var postponedCallbackValue1 = null;
function OnListBoxIndexChanged(s, e) {
    var item = ListBox.GetSelectedItem();
    if (CallbackPanel.InCallback())
        postponedCallbackValue = item.value;
    else
        CallbackPanel.PerformCallback(item.value);
}

function OnListBoxVslIndexChanged(s, e) {
    var item = ListBoxVsl.GetSelectedItem();
    if (CallbackPanel2.InCallback())
        postponedCallbackValue1 = item.value;
    else
        CallbackPanel2.PerformCallback(item.value);
}

function OnEndCallback(s, e) {
    if (postponedCallbackValue != null) {
        CallbackPanel.PerformCallback(postponedCallbackValue);
        postponedCallbackValue = null;
    }
}    

function OnEndCallback2(s, e) {
        if (postponedCallbackValue1 != null) {
        CallbackPanel2.PerformCallback(postponedCallbackValue1);
        postponedCallbackValue1 = null;
    }
}