if you 'RTFM' 
... the complex part was to get the right software and drivers in windows for the Nano and load the lib for the PS/2 (somehow it was copied to my Windows User profile and not in the LIB directory when I did the import.
Other thing that took some time is to find- out the correct wires and PINS. lucky I have a multi-meter, I Used a old joystick cable to find the correct wires.. Other thing that was a bit difficult was to get the correct pin settings on the USB mouse. I didn't know what was right or left. lucky I found out that the GND was also attached to the outside so I could find pin 1. Next thing that took some time was to find the right ports on the Nano (Especially CLK and DATA) But you told me it was D10 and D11 .. where D is digital
But the most scared moment was the moment that the thing must be connected to my MSX... 
.. First question that came to my mind was "Will it blowup my lovely Turbo-R or not" So to be sure I double checked everything .. and next thing I did was to find a old MSX (Toshiba HX-10), never used before, to see if it got some damage or not I used that MSX a bit like Animal Testing .. it passed .. and at least the MSX was running fine ...so .. then I tested it on my Turbo-r and MSX8280 etc. ..... So ....No it was not difficult.... but there were some moments of truth ... but if you take the time and think everything over sometime it's good to do as an beginner.. and the fun part was a big 10!
Oh!!! and don't forget the RESULTS
How many people can say on this forum that they have a scroll wheel in Symbos on the MSX
Nice pics! Nice project! 
For the wheelmouse I think both msx joystick ports are needed. It should be able to send the wheeldata as mouse movement (Y-axis) to second joystick port....??
.. the wheelmouse is already working .. with one joystick port ! Was that not clear in my movie ?
And in this movie from NYYRIKKI LINK
