virtual_column.i4.v = window_virtual_column_c(window_id.i2.v,
						      column.i4.v [,start.i4.v])

	This routine converts from a physical I/O window column value to a
	virtual column value in a horizontally scrolling window.

	window_id	ID of desired window
	column		physical I/O window column number
	[start]		first virtual column number (default is 1)

	This function returns status values as follows:

	CBS_INVARG		invalid window ID or column
	CBS_NO_WINDOW		window doesn't exist
	otherwise		corresponding virtual column number

	This function requires the following include files:

	cbslib_h, acnet_errors_h

	Related functions:

	window_physical_column_c, window_hscroll_c, window_tvm(_c),
	window_tvmx(_c), window_last_io_location_c, window_row_to_entry_c,
	window_entry_to_row_c, window_current_row_c,
	window_is_in_scroll_buffer_c, window_scroll(_c)

	C/C++ usage:

	short	window_id;
	int	virtual_column;
	int	column = 5;
	int	start = 1;

	virtual_column = window_virtual_column_c(window_id,column,start);