WoWInterface - System Message Parsing

I apologize if this has been answered else where but I have been unable to find what I am looking for.

I am looking to parse the name of the player (PlayerX) in each of the following system messages.

PlayerX is already in a group.
PlayerX declines your group invitation.
PlayerX joins the party.
PlayerX has joined the raid group
Cannot find 'PlayerX'.

I have some hacked together code that will do this below that I have taken from another mod. It takes the entire string from CHAT_MSG_SYSTEM and looks for the space in the first 4 cases or the ' in the last one and sends me back just the name.

Code:

function RN_GetArgs(message, separator)

        -- This procedure from DKP_System by Sammysnake

        -- Declare 'args' variable.

        local args = {};



        -- Declare 'i' integer.

        i = 0;



        -- Search for seperators in the string and return

        -- the separated data.

        for value in string.gfind(message, "[^"..separator.."]+") do

                i = i + 1;

                args[i] = value;

        end -- end for



        -- Submit the filtered data.

        return args;

end -- end RN_GetArgs()

Does Blizzard provide this information already in an arg that I am missing? Is there another/better Event that I could be looking at? Or is this the best way to obtain this information?

Any information greatly appreciated as this is my first shot at a 'real' mod.