How to simulate electron beam for vacuum tube devices in FEMLAB?

hi,anybody very familiar with FEMLAB(Multiphysics)?,im very new to this software,also im working in it to simulate electron beam for vacuum tube devices..is it possible to do this simulation in this software..pl do let me know..also any ideas and suggestion to pursue the simulation,i have found one example for electrostatic field generation..can it be useful for e beam generation?pl reply me as early as possible..