Eh that is nice !! But who was talking bout middle-mouse-button ? That should be no prob for every mouse-adapter as there is a dedicated input on the Amiga's mouseport.
Useing the scrollwheel on the other side requires some tricks.
I do have an microsyms and it has 2 distinct setting, one 3 buttons, no driver required and the other with scrollwhell-support, freewheel required.
What does freewheel do ? Well it boils down to the adapter sending pulses over the middle-button input and freewheel decoding them to up or down movements.
