Mouse Tracking
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The sample tracks the movement of mouse over a DataSeries Line.

Draws Horizontal and Vertical markers on the DataSeriese line.
Point on the Line is mapped with reference to the position of
the mouse cursor on the screen. It also draws an Ellipse around 
the intersection point.

Implementation uses the coordinates for the two DataPoints between
which lies the current mouse position. Based on the Line theorem,
coodinates of the current mouse position is mapped on the DataSeries
Line.