How to make borders without using parts?

So basically i want to make a invisible box border thing, but if i use invisible parts for some reason, it breaks the 3D atmosphere, basically making the sun invisible, and i dont want an invisible sun, so i need to use a script to get the X, Y and Z Co-Ordinates, basically if you go past the X Co-Ordinate of 500 for example, you die

I cant find any references so there is no base script :C