select_field_update_c

	status.i4.v = select_field_update_c(window_id.i2.v, select_id.i4.v,
					    entry_text.i1a.r)

	This routine services a selection field in a window created by an
	earlier call to select_field_init_c.  This should be called upon
	the receipt of a user interrupt event.

	window_id	ID of desired window (returned from prior call to
			window_construct(_c))
	select_id	ID of selection field type (returned from a prior
			call to select_field_register_c)
	entry_text	returned entry text

	This function returns status values as follows:

	CBS_INVARG		invalid select ID passed
	CBS_NO_SUCH		select field does not exist
	CBS_NOTENB		select field is disabled
	CBS_READONLY		no new entry selected
	otherwise		index of new entry selected

	This function requires the following include files:

	cbslib_h, acnet_errors_h

	Related functions:

	select_field_init_c, select_field_read_c, select_field_set_c,
	select_field_set_by_value_c, select_field_delete_c,
	select_field_register_c, select_field_enable_c,
	select_field_disable_c, select_field_text_to_id_c,
	select_field_display_info_c

	C/C++ usage:

	char	entry_text[ENTRY_LENGTH];
	short	window_id = WMNGR_BACKGROUND;
	int	status;
	int	select_id;

	status = select_field_update_c(window_id,select_id,entry_text);