Send addon message based on GUID?

[Chr0nicxHack3r]

Hello everyone! I am currently working on yet another call out addon. The problem I am having is that with my addon who ever in the raid/group has it and the settings on will make the call out. I am looking to make it so only 1 person does this call out.

I am new to all of this and would love some help! The process I am thinking that I can get it work would be like:
1. Get GUID of raid/group members
2. Determine lowest or highest GUID
3. Determined GUID makes call out

The biggest issue is this is far out of what I am capable of and been cracking at this for weeks. Would love some help in the right direction or some pointers to really get me going. I use Wowpedia for a reference on mostly what I am trying to do.

If easier I am more than happy to try an identify one person by something else if GUID is complicated, Such as taking that character name and using it alphabetically?