I'm not the owner, I just did this challenge and wondered why I have not found a checker for that. So I only can say what I think: The owner wants three consexutive GC codes and if this is because of some limitations not possible, it doesn't fit the rules of this challenge.
I think the script should only check if there are three finds with a consecutive GC-code anywhere in the world.
(Sorry for my bad English, school is long time ago :-) )