TRACKB ; trackball to navigate through an enlarged multi-subplot figure
-->suppose you have a layout of axes or subplots and you want
to see one or more axes magnified (i.e. the size of those subplots (h+w)
is enlarged, NOT parts of the subplot)

-use MOUSEWHEEL to increase/decrease width/hight of subplots/axes
(ZOOM-FUNCTION)
-use lower-left corner TRACKBALL to navigate through subplots/axes
-CONTEXTMENU to reset (zoomfactor=1)

USAGE
[1] plot a figure with subplots
[2] type TRACKB in commmand window
[3] activate TRACKB-PUSHBUTTON in the figure's toolbar
[4] NOW YOUR TURN: use mousewheel to increase/decrease the 'axes-layout',
i.e. all axes will be increased/decreased in width and hight
-a schematic draft in the lower left corner depicts the 'axes-layout'
-move red TRACKBALL on the drawing to move through axes

AN EXAMPLE IS PRESENTED IN THE FUNCTION

----------------------------------------------------------------------
Paul, BNIC 2010
----------------------------------------------------------------------