Unfortunately our devices were not designed as mice, but as navigation devices. Complementary to a mouse. With a mouse you can activate various menus in a program, or switch between different programs, while navigating with your SE (I suppose it is a SpaceNavigator SE).
1. It is possible to connect two mices. But unfortunately you have only one mouse cursor . And that's a problem.
2. Could you explain what do you mean to trigger SE?