Diode Diabolus

The question is entirely in the title however I'll give more detail. I'd love to Remap my (as default) sniper button to an extra exclusive mouse button (i.e. like the numpad mice have M1 through M9 mappable as exclusive keys for gaming (Dodge=M7). I can only seem to be able to map the sniper key as an existing key on my keyboard or mouse. Hopefully that makes sense. Or am I thinking that those keys exist when other users are likely just mapping existing keys to their numpads and making a fool of myself? 😂 Cheers in advance. 👍🏻😂