billythekid has already shown above that it can be done...
alias F1 echo -a My new F1 key function
yes, but I think you didn't entirely understood the issue ;-]
I know a little about those programs that help handicapped people use computers and usually they have shortcut keys bound to certain functions. most likely the program the person from the first post uses, uses F1-F12 for certain functions. so you should read the sentence as: the F1 key is now bound to 'help', could 'help' not be bound to another key thus freeing the F1 key for use by the helper program?
something like this can't be simply done by mIRC scripting because you can only redefine the key, not simply undefine the key ;-]