100分求大神相助

100分求大神帮助
System.Diagnostics.Process.Start(RichTextBox6.Text) '测试按钮

这个是在新窗口打开URL  有可以在原窗口打开的代码么（就是在当前活动的IE窗口内打开URL的代码） 请大神们帮帮忙  尽量详细点
[解决办法]
引用Interop.SHDocVw.dll

using System;
using System.IO;
using System.Windows.Forms;

namespace WindowsFormsApplication7
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void OpenUrl(string url)
        {
            SHDocVw.ShellWindows shellWindows = new SHDocVw.ShellWindowsClass();
            foreach (SHDocVw.InternetExplorer ie in shellWindows)
            {
                string filename = Path.GetFileName(ie.FullName).ToLower();
                if (filename.Equals("iexplore.exe"))
                {
                    object o = null;
                    ie.Navigate(url, ref o, ref o, ref o, ref o);
                    return;
                }
            }

            System.Diagnostics.Process.Start(url); 
 
        }

        private void button1_Click(object sender, EventArgs e)
        {
            OpenUrl("http://www.google.com");
        }
    }
}

Private Sub OpenUrl(ByVal url As String)
        Dim shellWindows As SHDocVw.ShellWindows = New SHDocVw.ShellWindows()
        For Each ie As SHDocVw.InternetExplorer In shellWindows
            Dim filename As String = Path.GetFileName(ie.FullName).ToLower()
            If filename.Equals("iexplore.exe") Then
                Dim o As Object = Nothing
                ie.Navigage(url, o, o, o, o)
                Return
            End If
        Next
        System.Diagnostics.Process.Start(url)
    End Sub