javascript for two listbox (move selected item from first listbox to second listbox)

<script type="text/javascript">
        function lstDblClicked() {
            var left_lst = document.getElementById("<%=_lbBox.ClientID%>");
            var right_lst = document.getElementById("<%=_lbBox0.ClientID%>");

            for (var i = 0; i < left_lst.length; i++) {
                if (left_lst.options[i].selected == true) {
                    right_lst.options[right_lst.length] =
            new Option(left_lst.options[i].text,
            left_lst.options[i].value);
                    left_lst.options[i] = null;
                    i = i - 1;
                }
            }
            return;
        }
    </script>
    <script type="text/javascript">
        function lstDblClicked1() {
            var left_lst = document.getElementById("<%=_lbBox.ClientID%>");
            var right_lst = document.getElementById("<%=_lbBox0.ClientID%>");

            for (var i = 0; i < right_lst.length; i++) {
                if (right_lst.options[i].selected == true) {
                    left_lst.options[left_lst.length] = new Option(right_lst.options[i].text, right_lst.options[i].value);
                    right_lst.options[i] = null;
                    i = i - 1;
                }
            }
            return;
        }
    </script>

<form id="form1" runat="server">
    <div>
        <asp:ListBox ID="_lbBox" runat="server" Height="100px" Width="100px">
            <asp:ListItem Value="1" Text="One" />
            <asp:ListItem Value="2" Text="Two" />
            <asp:ListItem Value="3" Text="Three" />
            <asp:ListItem Value="4" Text="Four" />
        </asp:ListBox>

        <asp:ListBox ID="_lbBox0" runat="server" ondblClick="RequestNoteSubjectSelectListbox_DoubleClick(this)"
            Height="100px" Width="100px">
            <asp:ListItem>vvvv</asp:ListItem>
        </asp:ListBox>
    </div>
    </form>