A physical and mathematical model is developed for the numerical simulation of electron transport in a multielectrode microcell with a circular emitter. Two circular grid electrodes are included in the model to control the electron beam. A target plate face electrode is considered as a secondary electron source. Electron beam transport in a self-consistent electric field is simulated using a cylindrical particle mesh code. Some typical examples are calculated to demonstrate the effectiveness of the proposed technique for optimization of beam control. The influence of a magnetic field on the static and dynamic characteristics of the microcell is also studied. Split anode difference current is predicted in a magnetic field and thus the microvacuum cell may be used as a magnetosensitive element.