Whilst the new Kensington Trackballworks software is Win 7 64-bit and allows easy redefinition of each trackball button, and the two upper buttons work fine in most Windows applications, nevertheless they are steadfastly ignored by Cubase 6.
If you want to regain the use of the upper buttons, then one answer is to use X-Mouse Button Control (free software) http://www.highrez.co.uk/downloads/XMouseButtonControl.htm . In the config GUI, “Middle button” refers to upper left trackball button, and “Mouse button 4” refers to the upper right. Unfortunately, you can’t use the “chord” facility where you hold two buttons at the same time to get a further function.
X-Mouse Button Control appears to be quite sophisticated in that you can set trackball button behaviour on a per application basis (via “profiles”) and within each profile up to five separate layers of button definitions can be navigated. You can read about it’s functionality here http://mirror.highrez.co.uk/downloads/X-Mouse%20Button%20Control%20User%20Guide.pdf .
I am in no way connected to the author of this software. I just found it on my internet travels and decided to use it. Your mileage may vary, as they say.