I have a Logitech Trackman Marble and I really love it. I spend a lot of time on web browser and code editors. I was wondering if there could be a feature like when I press Option Key the trackball becomes a scroll wheel. So that I can use the trackball for both moving cursor and scrolling.
You can use KeyRemap4MacBook:
Replace ModifierFlag::FN with VK_CONTROL for either control. Keys that aren't modifier keys can be mapped to EXTRA1:
Key Repeat > [Pointing Device] CursorMove to ScrollWheel Rate changes the scrolling speed.