el = ADDLISTENER(hSource, Eventname, callbackFcn) creates a listener
for the event named Eventname.  The source of the event is the handle 
object hSource.  If hSource is an array of source handles, the listener
responds to the named event on any handle in the array.  callbackFcn
is a function handle that is invoked when the event is triggered.
el = ADDLISTENER(hSource, PropName, Eventname, Callback) adds a 
listener for a property event.  Eventname must be one of
'PreGet', 'PostGet', 'PreSet', or 'PostSet'. Eventname can be
a string scalar or character vector.  PropName must be a single 
property name specified as string scalar or character vector, or a 
collection of property names specified as a cell array of character 
vectors or a string array, or as an array of one or more 
meta.property objects.  The properties must belong to the class of 
hSource.  If hSource is scalar, PropName can include dynamic 

For all forms, addlistener returns an event.listener.  To remove a
listener, delete the object returned by addlistener.  For example,
delete(el) calls the handle class delete method to remove the listener
and delete it from the workspace.
ADDLISTENER binds the listener's lifecycle to the object that is the 
source of the event.  Unless you explicitly delete the listener, it is
destroyed only when the source object is destroyed.  To control the
lifecycle of the listener independently from the event source object, 
use listener or the event.listener constructor to create the listener.
See also LISTENER, EVENT.LISTENER, SWPREF, NOTIFY, DELETE, META.PROPERTY, EVENTS Help for swpref/addlistener is inherited from superclass HANDLE
Reference page in Doc Center
   doc swpref/addlistener