Caputring Text From a 3rd Party RichEdit Chat Window

Question

Hi All, I want to capture / read the text flowing through a chat window that is part of an external application. I should note that I don't just want to capture the text in the chat window once, I want to get the new text as and when it is posted into the chat window I have little knowledge of the windows api so a simple explanation or sample code would be much appreciated. Adam