Load into ContentPlaceHolder asp.net

Question

I have an issue where I am using a master page.  I am loading content into the content place holder.  Based on what is selected in my datagrid it will do a response.write for a video to pop up.  My issue is the video loads into the top of the page before my masterpage.  I need the video to load into the contentplaceholder or another page would be fine.  Here is what I have right now:

 public partial class Videos1 : System.Web.UI.Page
{
    VideoDB objVideo;
    protected void Page_Load(object sender, EventArgs e)
    {
        lblMessage.Text = "";
        if (!Page.IsPostBack)
        {
            LoadVideo();
        }
    }

    protected void LoadVideo()
    {
        objVideo = new VideoDB();
        int nType = 1;
     
        if (Roles.IsUserInRole(HttpContext.Current.User.Identity.Name, "User 1"))
            nType = 1;
        else if (Roles.IsUserInRole(HttpContext.Current.User.Identity.Name, "User 2"))
            nType = 2;

        gv.DataSource = objVideo.GetVideoByType(nType);
        gv.DataBind();

       
    }
    protected void gv_RowCommand(object sender, GridViewCommandEventArgs e)
    {
        try
        {
            if (e.CommandName.Equals("PlayVideo"))
            {
                int nItemID = int.Parse(gv.DataKeys[0].Value.ToString());
                string sTitle = e.CommandArgument.ToString();

 

                objVideo = new VideoDB();
                SqlDataReader dBContent = objVideo.GetSingleVideo(nItemID);
                dBContent.Read();

                string sFileName = (String)dBContent["FileName"];

                SendEmail(txtName.Text.ToString(), txtEmail.Text, sTitle);

                   System.Text.StringBuilder sb = new System.Text.StringBuilder("<OBJECT ID='" +
                   this.ClientID + "' name='" + this.ClientID + "' " +
                   "CLASSID='CLSID:D27CDB6E-AE6D-11cf-96B8-444553540000'" + "codebase='http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=6,0,29,0'" +
                   "VIEWASTEXT" + "height=300 width= 300>");

                //Render properties as object parameters
                sb.Append("<PARAM name='movie' value='" + @"Video\" + sFileName + "'>");
                sb.Append("<PARAM name='quality' value='high'>");
                sb.Append("<embed src='" + @"Video\" + sFileName + "' quality=high pluginspage='http://www.macromedia.com/shockwave/download/index.cgi?P1_Prod_Version=ShockwaveFlash' type='application/x-shockwave-flash' width='320' height='240'></embed>");

                              
                  Response.Write(sb);
            }
        }
        catch
        {
            lblMessage.Text = "Error in processing request.";
        }
    }

 

My issue is with the Response.Write(sb);  I need it to load in my "ContentPlaceHolder1" container.