>I'm creating a Custom class to work with a grid at the same level. How can I get code into the MouseEnter and MouseLeave events of the grid at runtime? This class is meant to reside at the same level as the grid and the only known relationship between them at design time is that name of the grid is a property of the Custom class. I want all the rest of the stuff to happen at runtime.

As Sergey said, use BindEvent. Otherwise you can try to use custom class.