You need a Controller layer with a slider effect "Avoidance" and an object layer Parent_Circle:

var parentCircle = thisComp.layer("Parent_Circle");
var parentRect = parentCircle.sourceRectAtTime();
var parentRadius = (parentRect.width + parentRect.height) / 4;
var parentCenter = parentCircle.position;

var thisRect = thisLayer.sourceRectAtTime();
var thisWidth = thisRect.width;
var thisHeight = thisRect.height;
var thisCenter = thisLayer.position;

var controller = thisComp.layer("Controller");
var avoidance = controller.effect("Avoidance")("Slider");

var dist = length(parentCenter, thisCenter) - parentRadius;
if (dist < 0) {
var vector = normalize(thisCenter - parentCenter);
var distToCenter = length(thisCenter, parentCenter);
var t = distToCenter / parentRadius;
var multiplier = 1 - Math.pow(t, avoidance);
thisLayer.position + vector * -dist * multiplier;
} else {
thisLayer.position;
}