You would have to put your "hidden" code into a DLL itself. Even so, mIRC would still have to have the scripted code in it (visible) that will let it read the DLL and anyone with the slightest knowledge of scripting will be able to figure out how to get what they want out of the DLL by just changing the calling code in the visible script.
If you want commands in a script that you don't want anyone to know about unless they have some kind of level, you're not really going to manage that in a mIRC environment. mIRC is and always will be open scripting and there isn't really a good way to prevent anyone with a little knowledge of scripting to figure out whatever you do and change it. Either make different scripts that you only share with those who should have them, or else don't include commands/controls that are "secret" or whatever.
