reorder list OnItemReorder not fire

I have a reorder list:

<asp:ReorderList ID="ReorderList1" runat="server" AllowReorder="True"
        DataKeyField="Code" DataSourceID="AccessDataSource1" Font-Size="Large"
        Height="335px" PostBackOnReorder="False" SortOrderField="ListOrder" OnItemReorder="Change_List_Order"
        Width="551px">
        <ItemTemplate>
            <asp:Label ID="Label1" runat="server" Text='<%# Eval("ItemDesc", "{0}") %>'></asp:Label>
        </ItemTemplate>
    </asp:ReorderList>
    <asp:DragPanelExtender ID="ReorderList1_DragPanelExtender" runat="server"
        DragHandleID="ReorderList1" Enabled="True" TargetControlID="ReorderList1">
    </asp:DragPanelExtender>

Protected Sub Change_List_Order(ByVal e As ReorderListItemReorderEventArgs, ByVal sender As Object)

Msgbox ("Test message")

End Sub

The function Change_List_Order does not execute.  Anything I'm missing? Thx.