status.i4.v = whk_callback_init(oac_class.i4.v, whk_handler.f.v)

	This routine links redirected data acquisition changes to a
	user specified function.  The WHK Callback Facility will call the
	"whk_handler" function whenever an multicast message from a
	datapool contains a redirection change for the specified
	OAC class.  The "whk_handler" function is passed the class number,
	console number,	and a boolean reflecting whether redirection is 
	finished.  Interested users can discover more details of 
	redirection from dio_redirect_status.

	oac_class	Open Access Client class
			(constants are in oacdef)
	whk_handler	Handler function which is called back when 
			redirection involving this Open Access client
			has occurred.
			It has the following prototype:
			void whk_handler(int species, int numcns, int done)
				species		the class number
				numcns		is the console number
				done		TRUE when redirected finished

	This function returns ACNET status values as follows:

	OK			success
	CLIB_NOINIT		ACNET callback handle not established
	ACNET_xxx		error registering multicast

	This function requires the following include files:

	cnsparam_h, clib_h, oacdef_h, acnet_errors_h

	Related functions:


	C/C++ usage:

	int	status;
	int	oac_class = OAC_CLASS_MIRROR;		(Mirror, for example)
	void	whk_handler(int species, int numcns, int done);

	status = whk_callback_init(oac_class,whk_handler);