You can animate it with shape layers and a repeater. If you have you used expressions before, modifying a “drag me” expression on the radius or scale parameter will get you there too:
//applied to a blur effect, for example, causes the blur intensity to increase as the to points get closer;
point1=transform.position;
point2=thisComp.layer("dragme").transform.position;
delta=sub(point1,point2);
distance=length(delta);
linear(distance, 0, 80, 40, 0);
I can’t remember where I got the dragme expression, but I didn’t write it.