status.i4.v = window_scroll_block_c(window_id.i2.v, direction.i4.v,
					    top_row.i4.v, bottom_row.i4.v,
					    left_column.i4.v, right_column.i4.v)

	Scroll a portion of the window indicated by "window_id" up or down
	by one line.  The scrolling region will be bounded on the top by
	"top_row", on the bottom by "bottom_row", on the left by
	"left_column", and on the right by "right_column".  These are all
	in terms of the window's coordinate system.  The direction of the
	scroll is determined by "direction".

	window_id	window ID (use WMNGR_BACKGROUND for background window)
	direction	scroll direction
			(WMNGR_UP -> scroll text up,
			 WMNGR_DOWN -> scroll text down)
	top_row		top row of scrolling region
	bottom_row	bottom row of scrolling region
	left_column	left column of scrolling region
	right_column	right column of scrolling region

	This function returns ACNET status values as follows:

	OK			success
	CBS_NO_WINDOW		requested window does not exist
	CBS_INVID		invalid window ID
	CBS_INVARG		invalid row and/or column values
	CBS_NOT_IN_WINDOW	scrolling region extends outside of window

	This function requires the following include files:

	cbslib_h, acnet_errors_h

	Related functions:

	window_scroll(_c), intro_tv_windows

	C/C++ usage:

	short	window_id;
	int	status;
	int	direction = WMNGR_UP;
	int	top_row = 1;
	int	bottom_row = 10;
	int	left_column = 1;
	int	right_column = 20;

	status = window_scroll_block_c(window_id,direction,