In addition to our cell types, you can place your own controls on a sheet to provide
more interaction with the user. Anything that can be derived from the Control class
in the .NET framework can be hosted on a sheet in FarPoint Spread.
The child control is placed on a separate layer, the controls layer, that is separate
from the data area where cells are and is separate from the drawing layer wear shapes
and other graphical elements are.
The child control is one of any number of controls that can be placed on the sheet.
For the sheet there is a child control container (similar to the shape container
for all the shapes on the sheet). You can enumerate through each control and override
any property of the interface of that control. You can set events and work with