AE - PointAt

1) Create 3 nulls: Null_PointAt, Null_Base, Null_Target
2) Set the following transform expressions on Null_PointAt:

Position:
thisComp.layer("Null_Base").transform.position

Scale:
point1 = thisComp.layer("Null_Base").transform.position;
point2 = thisComp.layer("Null_Target").transform.position;
scl=length(point1, point2);
[scl, scl]

Rotation:
fromPoint = thisComp.layer("Null_Base").transform.position;
atPoint = thisComp.layer("Null_Target").transform.position;
Pointer3=lookAt(fromPoint, atPoint);
if(atPoint[1]<fromPoint[1]) [Pointer3[1]]-180; else [-Pointer3[1]];