This is definately not the best place for this sort of thing as this is the particleIllusion forum. You were probably directed here because particleIllusion is a program that could likely handle this sort of thing, and it is sheduled for release as a plug-in for After Effects in the near future (some time in june?).
If you are not using particleIllusion (which produces nice particle effects such as fireworks) you might try using the effect in after effects called “particle system 2”.
It’s not that simple to use, though it’s much easier to work with then “Particle Playground.” You might try asking for help in the AE forum specifically on the subject of that effect.
Aharon Rabinowitz
arabinowitz(AT)yahoo(DOT)com
http://www.allbetsareoff.com
http://www.pIllusionFusion.com