Partial update of parent page via AJAX (ASP.NET 2.0) on close of a child window - conditionally

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 System.Drawing;

public partial class ParentForm : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            //Set default values to the control on PageLoad for first time.
            lblChildWinValue.Text = "ChildWin Value: " + "NONE";
            lblCurrTime.Text = "CurrTime: " + DateTime.Now.ToString();
            lblPageLoadTime.Text = "PageLoadTime: " + DateTime.Now.ToString();
        }        
    }
    protected void btnHiddenForUpdate_ServerClick(object sender, EventArgs e)
    {        
        //Update Panels update - repopulate the controls the way needed.
        lblChildWinValue.Text = "ChildWin Value: " + "SOME VALUE";
        lblCurrTime.Text = "CurrTime: " + DateTime.Now.ToString();
        lblChildWinValue.BackColor = Color.Yellow;
        lblCurrTime.BackColor = Color.Yellow;

        //Just to show that this label wont update as outside the update panel
        lblPageLoadTime.Text = "PageLoadTime: " + DateTime.Now.ToString();
        lblPageLoadTime.BackColor = Color.Yellow;
    }
}