I'm assuming when you say "on open script" you mean when the "Scripts Editor" is open?
If this is indeed the case, then you might as well not even bother. Anyone who wants to alter or rip your files will do so. They don't even need mIRC to do it, they can open them in note pad and rip to their hearts content.
Aside from that, they could also just delete the file that is trying to "protect" your scripts.
With that said, if you are worried about someone ripping your code, the best option is to just not release it at all. Or just release it to really good friends that wouldn't give it to others.