Hi,

You can change the src propety dynamicly in the codebehind.

Html Code:

<object
classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000"
codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=7,0,19,0
width="560" height="340" style="width: 467px">
<param runat="server" id="paramVideoLink1" name="movie" value="http://www.youtube.com/v/84ZgMGtX7nE&hl=en_US&fs=1&>
<param name="allowFullScreen" value="true"></param>
<param name="allowscriptaccess" value="always"></param>
<embed runat="server" id="paramVideoLink2" src="http://www.youtube.com/v/84ZgMGtX7nE&hl=en_US&fs=1&" quality="high" pluginspage="http://www.macromedia.com/go/getflashplayer" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="560" height="340"></embed>
</object>

<asp:Button ID="ChangeFlvUrl" runat="server" Height="26px" onclick="ChangeFlvUrl_Click"
Text="Change flv url" Width="122px" />

CS Code:

protected void ChangeFlvUrl_Click(object sender, EventArgs e)
{
paramVideoLink1.Attributes.Add("value", "http://www.youtube.com/v/ac7aSF7ETtU&hl=en_US&fs=1&");
paramVideoLink2.Attributes.Add("src", "http://www.youtube.com/v/ac7aSF7ETtU&hl=en_US&fs=1&");
}

Please check the following link:

http://blogs.ugidotnet.org/kfra/archive/2006/10/04/50003.aspx