In Cubase SE3, you need to go to VST Connections and create 4 Stereo busses. In Cubase SE 3, you are limited to 4 total buses. If you create 4 stereo buses, you will be able to access 8 total inputs. When you create a Mono audio track in Cubase SE3, the inputs you will have available to select will be (Left 1, Right 2, Left 3, Right 4, Left 5, Right 6, Left 7 and Right 8 if you have 4 stereo busses created in VST Connections.