As a technique for compensating for tumor motion induced by respiratory and cardiac motions, various dynamic approaches are being investigated and implemented in radiation therapy. This paper presents a novel system that can continuously track the tumor during radiation dose delivery so that a precise dose is given to a moving target while reducing dose to nearby critical organs for improved patient treatment outcome. The efficacy of the proposed methodology has been investigated by extensive computer simulation using a Proportional, Integral and Derivative (PID) controller. System design and simulation results are presented in this paper.