Simulation of magnetic fields

Hello i need a code that can simulate magnetic fields in high voltage transmission line, im working on comparing real values provided by a company with simulated ones, i want to publish an article about that. The code preferible in MATLAB, MAPPLE, C++, FORTRAN, if you can provide it for me with a link i will apreciate it. Or if any of you know of a program that do the job that work to.