Multiselect DropDown ListBox Control for Web Applications

<%@ Control Language="c#" AutoEventWireup="false" Codebehind="MultiselectDropDownListBox.ascx.cs"
    Inherits="Controls.MultiselectDropDownListBox" TargetSchema="http://schemas.microsoft.com/intellisense/ie5" %>
<link media="all" href="Controls/CSS/MultiSelectListBox.css" type="text/css" rel="stylesheet">

<script language="javascript" src="Controls/Scripts/MultiSelectListBox.js"></script>

<asp:Panel ID="MSDDLB_pnl" BackColor="White" Width="186px" Height="0px" runat="server" HorizontalAlign="Left"> 
    <table id="MSDDLB_tbl" style="border-right: #6699ff 1px solid; table-layout: fixed;
        border-top: #6699ff 1px solid; border-left: #6699ff 1px solid; border-bottom: #6699ff 1px solid;
        height: 20px" cellspacing="0" cellpadding="0" width="100%" border="0" runat="server">
        <tr id="rowDD" style="height: 15px" runat="server">
            <td nowrap style="height: 15px; vertical-align: text-top;">
                <asp:TextBox ID="MSDDLB_txtbox" Style="cursor: default" runat="server" Width="100%"
                    ReadOnly="True" ToolTip="" Font-Size="Smaller" BorderColor="Lavender" BorderStyle="None"
                    Height="15px">Please select...</asp:TextBox>
                <input id="HdnField" type="hidden" runat="server" value="Please select ..." />
            </td>
            <td id="colDDImage" style="padding-right: 0px; padding-left: 0px; padding-bottom: 0px;
                padding-top: 0px; background-color: inactivecaptiontext; height: 15px; background-repeat: no-repeat;"
                background="Controls\Images\DDImageDown.bmp" width="18" runat="server">
            </td>
        </tr>
    </table>
    <div class="DropDownClosed" id="MSDDLB_div" runat="server" align="left">
        <asp:CheckBoxList ID="MSDDLB_cblst" OnSelectedIndexChanged="MSDDLB_cblst_SelectedIndexChanged"
            runat="server" Height="15px" Width="100%" Font-Names="Trebuchet MS" BackColor="#E0E0E0">
        </asp:CheckBoxList>
    </div>
    <iframe class="iFrameClosed" id="MSDDLB_iframe" frameborder="0" scrolling="auto"
        runat="server"></iframe>
</asp:Panel>