Having a script only work on a specified difficulty.

I need to know in order to finish my current map, how to get a script to only work on a certain difficulty. Right now I have:

if (GameSkill () == ?)
{
scripts
}

I've tried GAME_SKILL_EASY, GAME_EASY, and EASY, but none of them worked. What is the proper keyword? Also is Difficulty 3 NORMAL and Difficulty 4 HARD... I might need those someday. Thanks in advance.

EDIT: Never mind I got it. It was SKILL_EASY, but I would still like to know if Difficulty 3 is NORMAL and Difficulty 4 is HARD.

from zdefs.acs:

#define SKILL_VERY_EASY 0
#define SKILL_EASY 1
#define SKILL_NORMAL 2
#define SKILL_HARD 3
#define SKILL_VERY_HARD 4

Eeep, it has something for all 5. That's a surprise. Thanks Boris.