J3D zoom

I am using the OrbitBehavior Class to zoom in on my application. The
zoom action moves the ViewPlatform closer to or further from the point
of interest when the mouse is moved with the middle mouse button
pressed. I'd rather have a zoom in and zoom out button (JButton) where
each time I pushed it, it would zoom in or out. Is this possible in
J3D or do i need to stick with the mouse button?
http://dmi.ensica.fr/doc/Java/java3d-1_3_2-doc/com/sun/j3d/utils/behaviors/vp/OrbitBehavior.html

Thanks!
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