wn_unregister_function_c

	status.i4.v = wn_unregister_function_c(window_id.i4.v, type.i4.v,
					       callb_function.f.v
					       [,callb_data.g.v])

	This routine will remove a function previously registered by a
	call to wn_register_function_c.

	window_id	window ID
	type		type of function
			(WN_DESTRUCTOR_FUNC -> called when window is deleted,
			 WN_EXPOSE_FUNC -> called when the window is popped
					   to the top,
			 WN_OCCLUDE_FUNC -> called when the window is
					    occluded)
	callb_function	address of callback function to remove
	[callb_data]	address of callback data  (If this argument is not
			supplied, the first function matching "callb_function"
			will be unregistered.)

	This function returns status values as follows:

	OK			success
	CBS_INVARG		invalid window ID or function type was specified
	CBS_NO_WINDOW		requested window does not exist
	CBS_NO_SUCH		function not found
	CBS_MEMFAIL		dynamic memory allocation failure

	This function requires the following include files:

	cbslib_h, acnet_errors_h

	Related functions:

	wn_register_function_c

	C/C++ usage:

	int	status;
	int	window_id;
	int	type = WN_DESTRUCTOR_FUNC;
	void	callb_function(short window_id, void *callback_data);

	status = wn_unregister_function_c(window_id,type,callb_function);