Getting Interfaces to COM Object  IUnknown and IDispatch
Interfaces  When you invoke the actxserver or actxcontrol
functions, the MATLAB® software creates the server and returns a
handle to the server interface as a means of accessing its
properties and methods. The software uses the following process
to determine which handle to return:    1. First get a handle to
the IUnknown interface from the component. All COM components
are required to implement this interface.    2. Attempt to get
the IDispatch interface. If IDispatch is implemented, return a
handle to this interface. If IDispatch is not implemented,
return the handle to IUnknown.  Additional Interfaces
Components often provide additional interfaces, based on
IDispatch, that are implemented as properties. Like any other
property, you obtain these interfaces using the MATLAB get
function.  For example, a Microsoft® Excel® component contains
numerous interfaces. To list these interfaces, along with Excel
properties, type:  h = actxserver('Excel.Applicat