Read only help

Im not sure if this is even possible, but i would like to make a file what contains xml data permanently read only?

obviously you can right click on the file and set it to read only, but this is no good as someone else comes along, unticks and edits it..

may be it would help if i told you what im trying to do....

i design computer game levels for an online game , among with many others in the community.

the problem we have is people opening our maps , trying to edit them and breaking them.

im just trying to find a way to make them locked..

i can program in C++ so designing an application is not a problem... but i dont understand how a windows file is constructed, and how to disable the CheckBox for the read only attribute