make archimedean spiral

I am trying to figure out how to make a planar Archimedean spiral in EZNEC pro. I can figure out how to make a helix shape that is not planar but not a planar Archimedean spiral. The only way I see to do this so far is assemble a rectangular spiral out of many manually defined wires which seems miserable to do. There has to be a better way. Any suggestions would be appreciated.
Thanks!