Quick Question - Size of level

Hi,
just wondering where in the Rom code that the size of the level is determined.
In my program I want the user to be able set the location of an object in the level but stay within the bounds of the level.
Thanks
just wondering where in the Rom code that the size of the level is determined.
In my program I want the user to be able set the location of an object in the level but stay within the bounds of the level.
Thanks