如何获到其它进程鼠标选中的文字

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;

namespace WindowsApplication1
{
public enum ShellEvents
{
HSHELL_WINDOWCREATED = 1,
HSHELL_WINDOWDESTROYED = 2,
HSHELL_ACTIVATESHELLWINDOW = 3,
HSHELL_WINDOWACTIVATED = 4,
HSHELL_GETMINRECT = 5,
HSHELL_REDRAW = 6,
HSHELL_TASKMAN = 7,
HSHELL_LANGUAGE = 8,
HSHELL_ACCESSIBILITYSTATE = 11
}
public partial class Form1 : Form
{

[DllImport("user32.dll")]
public static extern int RegisterWindowMessageA(string lpName);

[DllImport("user32.dll")]
public static extern int DeregisterShellHookWindow(IntPtr handle);

[DllImport("user32.dll")]
public static extern int RegisterShellHookWindow(IntPtr handle);

[DllImport("user32.dll")]
public static extern IntPtr GetForegroundWindow();

[DllImport("user32.dll")]
public static extern int SetForegroundWindow(IntPtr handle);

private int uMsgNotify;
public IntPtr lastWindows;

public Form1()
{
InitializeComponent();
}

private void button3_Click(object sender, EventArgs e)
{
SetForegroundWindow(lastWindows);
System.Threading.Thread.Sleep(100);
SendKeys.Send("^c");
System.Threading.Thread.Sleep(100);

IDataObject oData = Clipboard.GetDataObject();
if (oData.GetDataPresent(DataFormats.Text))
this.textBox1.Text = (String)oData.GetData(DataFormats.Text);
else
this.textBox1.Text = "Not Data";

}

private void Form1_Load(object sender, EventArgs e)
{
this.TopMost = true;
uMsgNotify = RegisterWindowMessageA("SHELLHOOK");
RegisterShellHookWindow(this.Handle);
}

protected override void WndProc(ref Message m)
{
if (m.Msg == uMsgNotify)
{
switch (m.WParam.ToInt32())
{
case (int)ShellEvents.HSHELL_WINDOWACTIVATED:
IntPtr current = GetForegroundWindow();
Console.WriteLine("window activated:" + current.ToString());
if (current != IntPtr.Zero && current != this.Handle)
lastWindows = current;
break;
default:
break;
}
}
base.WndProc(ref m);
}

private void Form1_FormClosed(object sender, FormClosedEventArgs e)
{
DeregisterShellHookWindow(this.Handle);
}
}

}