control.GetHighPart(nValue)

	Purpose		Get the high-order 4 byte of a 8 byte value.
	Parameter
		nValue Double	8 byte value, whose high-order part shall be returned.
	Return value		A 4 byte value, which is the high-order part of the function's argument nValue.
	Remarks		You may use this function to retrieve the end index of data points, which are covered by a magnifier or zoom rectangle. See Zoom and Magnifier, fourth paragraph, for more informations.