The simple answer, as mentioned is "no." To further answer your question, all scripts can be viewed by anyone using them if they are loaded into mIRC. There is no way around that. You *can* make a DLL that does most of the work and then use a script that calls the DLL, but the script itself can still be viewed/changed. You could also purposely obfuscate your code (make it hard to read) by making simple commands much more complex than necessary, but anyone who knows how to script could still figure if s/he wanted to.
Scripting is rarely meant to be "secret". Anything scripted is usually going to be open to anyone with access to the file. If you want something that cannot easily be viewed by anyone with the file, use a programming language that is compiled.