Dusty planetary disks can form quickly around young stars and linger, despite the depletion of dust through mechanisms such as Poynting-Robertson drag. Planetesimals in the disk can replenish the dust with an efficiency that depends on their mass and velocity distributions. Here, we describe a numerical program to track the evolution of planetesimals through merging, fragmentation and drag. Our current effort is focused on coupling a Fokker-Planck solver with N-body calculations to follow the detailed behavior of larger planetesimals. Our results demonstrate the importance of gravitational stirring in dust production. Furthermore, stirring by planets larger than Pluto can generate the large scale heights seen in several dusty disks.