Illustrator Scripting :: Move Direction Handles In Sync With Anchor Point?

I'm trying to nudge the anchor points on an object randomly (to get an informal look). (I know some Effects do this already.)
 
Maintaining corner points is no problem - you just set the direction handles to the same coordinates as their anchor.
 
But I can't nudge a smooth point in the way I want to, which is to move the anchor but maintain the direction handles in exactly the same relation to their anchor as they had before. That is to say, they should remain smooth points.
 
My script calculates the difference between 'before' and 'after' positions of the anchor, and applies that difference to the direction handles… but in practice the smooth points are converted to corners, because the direction handles don't maintain their relation with the anchor.
 
var docRef = activeDocument;
var objects = activeDocument.selection.length;
var cShift = prompt("Point shift (pt)",5);
// loop through all objects
for(var count=0;count<objects;count++)

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