There is a single routine in the EZ widget library for adding widget callbacks.
void EZ_AddWidgetCallback(EZ_Widget *widget, int which_list
EZ_CallBack callback, void *data, int where)
This function registers a callback to the specified callback list.
To remove a specific callback from a callback list, use
void EZ_RemoveWidgetCallback(EZ_Widget *widget, int which_list
EZ_CallBack callback, void *data)
This function removes the specified callback if both the procedure and the registered data match.
To remove all callbacks on a callback list, use
void EZ_RemoveAllWidgetCallBacks(EZ_Widget *widget, int which_list)
This function clears the specified callback list of a widget.