  It is widely recognized that good jet energy resolution is one of the most
important requirements to the detectors for the future linear $e^+e^-$ collider
experiments. The Particle Flow Analysis (PFA) is currently under intense
studies as the most promising way to achieving the best attainable resolution.
In order to clarify the fundamental limits on the jet energy resolution with
the PFA, we have developed a set of C++ classes that facilitates history
keeping of particle tracks within the framework of Geant4. In this paper this
software tool is described and applied to a generic detector model so as to
identify fundamental limiting factors to the PFA performance.
