if you have your buttons set up like i do with a macro for every button on the mouse being a single keystroke then you're either going to have to make keymaps for every custom letter/number, or you're going to have to do what i do and use isboxer like keyclone lol

odds are you're not passing the keystrokes because isboxer isnt recognizing the keypress because its not in your keymaps lax can prolly explain this better but if you know much about isboxer you could do it too