	(SCALAR ADVERB)

	VCLICK is set by CLICK.  It corresponds to the value that 
	the function VCUR would have returned at the crosshair location 
	when the user clicks a mouse button.

	For a plot made with SHOW, this is the velocity in km/s (LINE), 
	or the position relative to the start of the scan in degrees 
	(CONDAR), and for a 2-d plot, this is the x-axis value.

