This is a general-purpose code that lets you disable any given button on the control pad. I've set it up so that you can see which bits are being reset every frame in the manner that they're shown in the RAM map.
This doesn't always work properly. You reset $15 and $17, but not $16 and $18. This means that anything which checks for the first frame of the button press (such as jumping or dropping an item from the reserve box) will not actually be disabled. If this is intentional behavior, which I highly doubt, please note it in the description and resubmit this.
This code is also very simple, but I don't see why we should trouble newbies by rejecting it just for that reason. That, however, creates usability problems - someone who can't recreate this on their own probably won't be able to figure out how to configure the bitfields. I think it'd be much nicer to make each button a separate define, then calculate the appropriate value based on those. Another suggestion would be to allow disabling A or B individually (currently, you either have to disable both by setting !Button1 to $80 or remap A to B by setting !Button2 to $80), which would make this code more useful.