Hooking outgoing chat messages

To modify outgoing chat messages we are going to hook the ChatEdit_ParseText function. However, this function also handles macros; so to avoid tainting we must use hooksecurefunc() to hook the function properly. Otherwise, your macros will no longer work.
 -- Place this code in the OnLoad function of your addon
 hooksecurefunc('ChatEdit_ParseText',MyAddon_ParseText);
MyAddon_ParseText will now be called after ChatEdit_ParseText has had a chance to handle macros and slash commands.
 function MyAddon_ParseText(chatEntry, send)
 -- This function actually gets called every time the user hits a key. But the
 -- send flag will only be set when he hits return to send the message.
 if (send == 1) then
 local text = chatEntry:GetText(); -- Here's how you get the original text
 local newText = text; -- here's where you can modify the text to your liking
 chatEntry:SetText( newText ); -- send the new text back to the UI
 end
 end