I want to use a PIC 16F877 microcontroller to detect the speed and position
of an object passing through a 3' x 3' opening.  Does the following design
have merit or is there a better way:

  Utilize a number of common Laser Pointers and associated infrared
detectors to form a grid.  When an object, say approximately 2", passes thru
the grid the PIC will detect the presence of an object (via input port state
change), and by processing this information, the PIC should be able to
determine relative position in the opening and also the approximate speed of
the object as it passes thru the Laser pointers beams.

What do you think?