electrode - voltage response to remote current

Hello,

I am trying to do a test on a probe with some electrodes in it. I am trying to have a current at a point 100 um away from the probe and record the voltage at the electrode. I have built the model but I cannot figure out how to get the tests to work. I'm not sure if I should use electrostatics or electric currents. The model is attached. Its a little confusing because I have done a lot of things to try and get it to work. Please help!! If you need more information just let me know.

Thanks!