I am trying to dynamically change the url link of an embeded youtube video from the code-behind on our website.

I am trying to dynamically change the url link of an embeded youtube video from the code-behind on our website.
Here is the HTML code for the video:
<ajax:TabPanel runat="server" ID="Panel5" HeaderText="Videos">
        <ContentTemplate>
            <table>
                <tr>
                    <td style="width:425px;">
                        <object width="425" height="344">
                        <param name="movie" value="http://youtube.com/myvideo/"/>
                        <param name="allowFullScreen" value="true"/>
                        <param name="allowscriptaccess" value="always"/>
                        <embed src="http://youtube.com/myvideo/" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed>
                        </object></td>
                </tr>
            </table>
        </ContentTemplate>
    </ajax:TabPanel>

using System;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.ComponentModel;
using System.Text;

namespace Backbone.UserControls
{
    /// <summary>
    /// A component for embedding a Windows Media Player in a web form.
    /// </summary>
    [DefaultProperty("Text"),
        ToolboxData("<{0}:MediaPlayer runat=server></{0}:MediaPlayer>")]
    public class MediaPlayer : System.Web.UI.Control
    {
        #region Public Properties
        private string _fileName = "";

        [Bindable(true), Category("Appearance"),
        Description("URL to a sound file")]
        public string Filename
        {
            get
            {
                return _fileName;
            }

            set
            {
                _fileName = value;
            }
        }

        private bool _autoStart = true;

        [Bindable(true),
        Category("Behavior")]
        public bool autoStart
        {
            get
            {
                return _autoStart;
            }

            set
            {
                _autoStart = value;
            }
        }

        private bool _Enabled = true;

        [Bindable(true),
        Category("Behavior")]
        public bool Enabled
        {
            get
            {
                return _Enabled;
            }

            set
            {
                _Enabled = value;
            }
        }

        private bool _enableContextMenu = true;

        [Bindable(true),
        Category("Behavior"),
        Description("Right-click menu visibility")]
        public bool EnableContextMenu
        {
            get
            {
                return _enableContextMenu;
            }

            set
            {
                _enableContextMenu = value;
            }
        }

        private bool _fullScreen = false;

        [Bindable(true),
        Category("Behavior")]
        public bool fullScreen
        {
            get
            {
                return _fullScreen;
            }

            set
            {
                _fullScreen = value;
            }
        }

        private int _Balance = 0;

        [Bindable(true),
        Category("Behavior"),
        Description("-100=left, 100=right, 0=balanced (default)")]
        public int Balance
        {
            get
            {
                return _Balance;
            }

            set
            {
                if (value >= -100 && value <= 100) _Balance = value;
                else throw new ArgumentException("Value must be between -100 and 100");
            }
        }

        private int _Volume = 100;

        [Bindable(true),
        Category("Behavior"),
        Description("0=mute, 100=full volume (default)")]
        public int Volume
        {
            get
            {
                return _Volume;
            }

            set
            {
                if (value >= 0 && value <= 100) _Volume = value;
                else throw new ArgumentException("Volume must be between 0 and 100");
            }
        }

        private int _Loop = 1;

        [Bindable(true),
        Category("Behavior"),
        Description("How many times to replay.")]
        public int Loop
        {
            get
            {
                return _Loop;
            }

            set
            {
                if (value >= 1 && value <= 10000) _Loop = value;
                else throw new ArgumentException("Value must be between 1 and 10000");
            }
        }

        private double _Rate = 1;

        [Bindable(true),
        Category("Behavior"),
        Description("Playback speed, 0.5 to 2.0")]
        public double Rate
        {
            get
            {
                return _Rate;
            }

            set
            {
                if (value >= 0.5 && value <= 2) _Rate = value;
                else throw new ArgumentException("Value must be between 0.5 and 2.0");
            }
        }

        private bool _Invisible = false;

        [Bindable(true),
        Category("Appearance"),
        Description("If false player will be invisible but can still play.")]
        public bool Invisible
        {
            get
            {
                return _Invisible;
            }

            set
            {
                _Invisible = value;
            }
        }

        private bool _buttonsVisible = true;

        [Bindable(true),
        Category("Appearance")]
        public bool ButtonsVisible
        {
            get
            {
                return _buttonsVisible;
            }

            set
            {
                _buttonsVisible = value;
            }
        }

        private bool _stretchToFit = true;

        [Bindable(true),
        Category("Appearance")]
        public bool StretchToFit
        {
            get
            {
                return _stretchToFit;
            }

            set
            {
                _stretchToFit = value;
            }
        }

        private int _Height = 300;

        [Bindable(true),
        Category("Layout")]
        public int Height
        {
            get
            {
                return _Height;
            }

            set
            {
                if (value >= 0 && value <= 10000) _Height = value;
                else throw new ArgumentException("Value must be between 0 and 10000");
            }
        }

        private int _Width = 300;

        [Bindable(true),
        Category("Layout")]
        public int Width
        {
            get
            {
                return _Width;
            }

            set
            {
                if (value >= 0 && value <= 10000) _Width = value;
                else throw new ArgumentException("Value must be between 0 and 10000");
            }
        }
        #endregion

        protected override void Render(HtmlTextWriter output)
        {
            //output begin object tag
            StringBuilder sb = new StringBuilder("<OBJECT ID='" +
                this.ClientID + "' name='" + this.ClientID + "' " +
                "CLASSID='CLSID:6BF52A52-394A-11d3-B153-00C04F79FAA6'" +
                "VIEWASTEXT" +
                " height=" + _Height + " " + "width=" + _Width +
                ">");

            //Render properties as object parameters
            sb.Append("<PARAM name='URL' value='" +
                _fileName + "'>");
            sb.Append("<PARAM name='AutoStart' value='" +
                _autoStart.ToString() + "'>");
            sb.Append("<PARAM name='balance' value='" +
                _Balance + "'>");
            sb.Append("<PARAM name='enabled' value='" +
                _Enabled.ToString() + "'>");
            sb.Append("<PARAM name='fullScreen' value='" +
                _fullScreen.ToString() + "'>");
            sb.Append("<PARAM name='playCount' value='" +
                _Loop.ToString() + "'>");
            sb.Append("<PARAM name='volume' value='" +
                _Volume + "'>");
            sb.Append("<PARAM name='rate' value='" +
                _Rate + "'>");
            sb.Append("<PARAM name='StretchToFit' value='" +
                _stretchToFit.ToString() + "'>");
            sb.Append("<PARAM name='enabledContextMenu' value='" +
                _enableContextMenu.ToString() + "'>");

            //Determine visibility
            if (_Invisible)
            {
                sb.Append("<PARAM name='uiMode'");
                sb.Append(" value='invisible'>");
            }
            else
            {
                if (_buttonsVisible)
                {
                    sb.Append("<PARAM name='uiMode'");
                    sb.Append(" value='full'>");
                }
                else
                {
                    sb.Append("<PARAM name='uiMode'");
                    sb.Append(" value='none'>");
                }
            }

            // Now render properties as an embed  tag for firefox, netscape, etc.
            sb.Append("<EMBED type='application/x-mplayer2' pluginspage='http://microsoft.com/windows/mediaplayer/en/download/'");
            sb.Append("id='").Append(this.ClientID).Append("' name='mediaPlayer' ");
            sb.Append("displaysize='4' autosize='0' showcontrols='1' showtracker='0' showdisplay='0' showstatusbar='1' videoborder3d='0' ");
            sb.Append("width='").Append(_Width).Append("' height='").Append(_Height).Append("' ");
            sb.Append("src=\"").Append(_fileName).Append("\" autostart='").Append(_autoStart).Append("' ");
            sb.Append("designtimesp='5311' loop='0'></EMBED>");

            //output ending object tag
            sb.Append("</OBJECT>");

            //flush everything to the output stream
            output.Write(sb.ToString());
        }
    }
}

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="PlayVideo.aspx.cs" Inherits="PlayVideo" %>
<%@ Register Namespace="Backbone.UserControls" TagPrefix="cc" %>
<!DOCTYPE html  PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <%--<cc:mediaplayer id="mediaplayer1" runat="server" filename="Videos/intro.wmv" width="500" height="400" />--%>
        <%--<cc:mediaplayer id="player1" runat="server" filename="winvideo-cs2k7-ordersextensibility.wmv" width="500" height="400" />--%>
        <asp:Panel ID="pnl1" runat="server"></asp:Panel>
    </div>
    </form>
</body>
</html>
 
 
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using Backbone.UserControls;

public partial class PlayVideo : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        MediaPlayer mp = new MediaPlayer();
        mp.Filename = "Videos/intro.wmv";
        //mp.Filename = "WinVideo-CS2K7-OrdersExtensibility.wmv";
        pnl1.Controls.Add(mp);
    }
}