Polyline Attractors on topography

Dear All,

I've been tweaking the Magnetic Displacement definition by Daniel Piker in the last couple of days to create a topographical landscape - I'm using point attractors on a grid of points and the resulting vector creates the Z height of the topography.
However I've been running into problems. When I try to add in an attractor that is based on a line (that evaluates between the original UV grid of a referenced surface and the line using CrvCP) the result is a really high uniform field. I'm trying to get the edge of the surfaces to behave like a 'wall' so that the edge rises steeply to the edge of the surface. Can anyone please take a look at the definition and point out if theres anything wrong, eg the 'pull' from that line attractor needs a limiter of some sort?
Any help would be greatly appreciated!

Thanks

Ben