In case it helps, I cleaned up the expression so its not referencing sliders..
start = 2000;
end = 700;
C = thisComp.layer(“HandyCam_Camera”);
CameraPos = C.toWorld([0,0,0]);
LayerPos = toWorld(anchorPoint);
Difference = length(CameraPos, LayerPos);
ease(Difference, start, end, 30, 0)