怎样控制WPF GroupBox.HeaderTemplate中的控件

Window1.xaml：

<Window x:Class="WpfApplication1.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Window1" Height="300" Width="300" Loaded="Window_Loaded">
    <Grid>
        <StackPanel>
            <GroupBox Name="GroupBoxUC" MinHeight="100">
                <GroupBox.HeaderTemplate>
                    <DataTemplate>
                        <DockPanel Name="dockbutton" HorizontalAlignment="Right">
                            <TextBlock Name="txtHeader" Text="header"  Foreground="Red"/>
                            <Button MinHeight="20" Width="50" Content="后 退"  Click="btnBack_Click" Name="btnBack"/>
                            <Button MinHeight="20" Width="50" Content="前 进"  Click="btnForward_Click" Name="btnForward"/>
                        </DockPanel>
                    </DataTemplate>
                </GroupBox.HeaderTemplate>
            </GroupBox>
        </StackPanel>
    </Grid>
</Window>

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Window1.xaml.cs：

 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace WpfApplication1
{
    /// <summary>
    /// Window1.xaml 的交互逻辑
    /// </summary>
    public partial class Window1 : Window
    {
        private Button btnBack;
        private Button btnForward;
        private TextBlock txtheader;

        public Window1()
        {
            InitializeComponent();
        }

        private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            Border headborder = (Border)GroupBoxUC.Template.FindName("Header", GroupBoxUC);
            ContentPresenter headContentPresenter = (ContentPresenter)headborder.Child;

            DataTemplate datatemp = GroupBoxUC.HeaderTemplate;

            txtheader = (TextBlock)datatemp.FindName("txtHeader", headContentPresenter);
            btnBack = datatemp.FindName("btnBack", headContentPresenter) as Button;
            btnForward = datatemp.FindName("btnForward", headContentPresenter) as Button;

        }

        private void btnBack_Click(object sender, RoutedEventArgs e)
        {
            txtheader.Text = "后退！";

            btnBack.IsEnabled = false;
            btnForward.IsEnabled = true;
        }

        private void btnForward_Click(object sender, RoutedEventArgs e)
        {
            txtheader.Text = "前进！";

            btnForward.IsEnabled = false;
            btnBack.IsEnabled = true;
        }

    }
}

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资料：http://social.msdn.microsoft.com/Forums/en-US/wpf/thread/d8fd2289-d8b9-447f-8d04-9557bd3ccda3