The problem is that the wheel is not working in MUI programs or anywhere else. Does anyone know how to make it work?
Not sure if you meant to post in this thread? To use a mouse with a scroll wheel effectively on a classic Amiga, you need a utility like Freewheel. I can't speak for all hardware but it works great with my Cocolino and PS/2-style optical mouse with scroll wheel. You can download it from Aminet, here:
http://aminet.net/package/util/mouse/FreeWheel