Maya Particle change instance geometry in certain places
 

Hello,

I am trying to make a simple Particle simulation where the particles change instance geometry, for example:
They start as cubes then when they are fall in the left side hole they became spheres and when the particles fall in the right side they became cylinders at the end when they exit the holes they became a donut shapes.
How to do that?
(In the attachment there is an image explanation)

if anyone interested to make such thing, I found the answer here
http://forums.cgsociety.org/showthread.php?p=8319807