I am not really to sure about scripting functionality for this, but in terms of the control for an object I believe you need to look at "object orientation" -- if you select an object this can be found in the Selection Information panel.

I'll investigate further and see what I can work out...

Okay I have found out that apparently there isn't a specific script function that will do this, but I was given the following example function that would do the job:

function MoveObjectByNormal(distance)
  nx, ny, nz = get("object.normal", objIndex)
  cmd("object.move", objIndex,
  nx*distance, ny*distance, nz*distance)
end

Hope this helps.