Functional electrical stimulation is a powerful tool for restoration of function after nerve injury. However selectivity of stimulation remains an issue. This paper presents an alternative stimulation technique to obtain fiber size-selective stimulation of nerves using FDA-approved electrode implants. The technique was simulated for the ventral roots of Xenopus Laevis, motivated by an application in bladder control. The technique relies on applying a high frequency alternating current to filter out action potentials in larger fibers, resulting in selective stimulation of the smaller fibers. Results predict that the technique can distinguish fibers with only a 2 μm difference in diameter (for nerves not exceeding 2mm in diameter). The study investigates the behaviour of electrically blocked nerves in detail. Model imperfections and simplifications yielded some artefacts in the results, as well as unexpected nerve behaviour which is tentatively explained.