Tracking puppet pin tool with null object track(HELP)

I'm trying to track my puppet pin tool to a null object.

I am using the code

n=thisComp.layer("NullObject_Name");
nullpos=n.toComp(anchorPoint);
fromComp(nullpos);

But ever time I assign the name of the null obect tp the puppet pin (eg. hair_bottom_left0)

n=thisComp.layer("hair_bottom_left0");
nullpos=n.toComp(anchorPoint);
fromComp(nullpos);

The pin tracks a different position and not the null object.

How do I get the pin to track to the null object I assigned it too?