1. An external control device for use with a neurostimulator coupled to a plurality of electrodes capable of conveying electrical stimulation energy into tissue in which the electrodes are implanted, comprising: output circuitry configured for transmitting sets of stimulation parameters to the neurostimulator; a user interface including a display device and at least a first control element configured to be actuated to selectively place the external control device between a first mode and a second mode; and a processor, when the external control device is in the first mode, configured for simulating a volume of tissue activation using a computational modeling technique for each of a first one or more candidate stimulation parameter sets, while preventing the output circuitry from transmitting the first one or more of candidate stimulation parameter sets to the neurostimulator, and when the external control device is in the second mode, configured for allowing the output circuitry to transmit a second one or more of candidate stimulation parameter sets to the neurostimulator.