Sure no problem.
I can explain what the operator is doing, it should be pretty straight forward:
The Plane has an animated gradient ramp on it. The Data Op is looking at the Plane (Select Object), it is looking for Point Color (Geometry->Closest Point by Surface + Geometry->Point Color). What that means is were a Particle is intersecting with the Plane that is the Point and at that Point the sub-op is looking for a Color. Since Color is a point3 or a Vector [R,G,B], we only need greyscale which just happens to be the Length of that Color vector (Convert->Vector to Real - Length) So now we have something that reads the greyscale color that is traveling across the plane. When that Color changes at the Point of the Particle it will trigger a Condition True/False (Condition->Is Greater than A) If the condition is met the Particle is sent to the Output.
I have a few Box#3/ADM tutorials on my vimeo page (mostly examples with scene files) Anselm aka Psychosilence has some great tutorials and DVDs, ParticleSkull also is coming out with some really cool tuts too. There was a user here 3ak who had some really cool setups, super smart dude (assuming he was a dude, may have been a dudette always hard to tell with anonymous users) haven’t seen them around in a while but searching should show some of their stuff.
If your fragments have an animated gradient on them I will make another example. The idea would be relatively close to the same.