Dynamically change embed video link

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">
                    &nbs ...