How to read the contents of a screen from another application [Office Communicator]

Knowing the hwnd of the window, how do I read the contents of this? Before anyone ask me, I'm trying to get the text that was used in the Communicator window.

Below is the code I found on the Internet. The code is not mine.

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;

namespace EventFun
{
class EventHookUp
{
    CommunicatorAPI.Messenger mCommunicator = null;

    static void Main(string[] args)
    {
        EventHookUp hu = new EventHookUp();
        hu.InitializeEventHocks();
        Console.ReadKey();
    }

    public void InitializeEventHocks()
    {
        mCommunicator = new CommunicatorAPI.Messenger();
        mCommunicator.OnIMWindowCreated += new CommunicatorAPI.DMessengerEvents_OnIMWindowCreatedEventHandler(mCommunicator_OnIMWindowCreated);
        mCommunicator.OnIMWindowDestroyed += new CommunicatorAPI.DMessengerEvents_OnIMWindowDestroyedEventHandler(mCommunicator_OnIMWindowDestroyed);
    }

    void mCommunicator_OnIMWindowCreated(object pIMWindow)
    {
        CommunicatorAPI.IMessengerConversationWndAdvanced stpIMWindow = pIMWindow as CommunicatorAPI.IMessengerConversationWndAdvanced;
        //stpIMWindow.History;
        long Hwnd = (long)stpIMWindow.HWND;
        Console.WriteLine("New IM Window Created : {0}", Hwnd);

        CommunicatorAPI.IMessengerContacts contactList = (CommunicatorAPI.IMessengerContacts)stpIMWindow.Contacts;
        StringBuilder sb = new StringBuilder();
        foreach (CommunicatorAPI.IMessengerContact imc in contactList)
        {
            sb.Append(imc.FriendlyName);
            sb.Append(Environment.NewLine);
        }
        Console.WriteLine(sb.ToString());
    }

    void mCommunicator_OnIMWindowDestroyed(object pIMWindow)
    {
        Console.WriteLine("IM Window Destroyed.");
    }
}
}

It sounds like you are trying to get the conversation text history from the conversation window? If so, George Durzi has an excellent blog post on this.