[Grimcat]

I am trying to figure out how to cause my character to act upon a specific whisper. I can figure out the LUA string parsing but I am new to WoW interface mod and do not know how to capture a whisper to parse. It looks like I would use the CHAT_MSG event? For instance I want to script so that when my friend to sends me a whisper tell that says: "GRIM HEAL" my character will automatically target and heal him. The code for casting a spell seems straight forward I just need to figure out how to capture the last whisper sent to me to check it for certain phrases.
Thx for any help!