You would need a copy of the source code (you can get that from CloneKey web site) and you need to have developer tools installed. https://developer.apple.com/technologies/mac/

This used to be free for everyone. But I think they may charge a small fee for it now.

If you are familiar with code or scripting I could probably help you through it. It was a set of three if statements to bypass the key sending event if the keystroke was one of those you wanted blacklisted.

After editing the code you use developer tools to compile or build the program.

I'll dig through the old code and see if I can find it again. It has been a while since I boxed on a Mac.