Electrical resistance in a structure

hello everybody,
I need to have a simulation of electrical potential in 1D beam elements in a structure. I want to give potential to one point of the model and ground to another point and observe the current flow inside the beam. in fact I need to calculate the whole electrical resistance inthe structure.
when I use Electrical Current in AC/DC module, it tells me that it is not applicable to select a point as a "point electric potential" or "point ground".
I have attached a picture of a sample structure.
How can I do this. should I use another module?

Thanks in advance
Ehsan