Two objects colliding

If I have two objects colliding, is there a way to get them to add their scale and combine into one object? So say you have two balls that are attracted to eachother and when they collide they run turn into one ball that has their total mass and their scale is added together?

The most obvious solution would probably be to destroy the original two objects and create a new object (from a prefab and/or procedurally) that has the characteristics you want.

Ok so i've got them randomly spawning at varous sizes and I'm just trying to get a new prefab to spawn where they collide with the scale added together.

var numberofpartices= 10;
var particles: Transform;
var seperation= Random.Range (-10,10);
var particlemaxsize=5;

function Start () {

for (var i : int = 0;i < numberofpartices; i++) {
var numRandom: int = (Random.Range(0,10)+.5);
var particleMade= Instantiate (particles, Vector3(i*seperation, 0, i*seperation), Quaternion.identity);
particleMade.transform.localScale= Vector3.one *numRandom;
}

}

function OnCollisionEnter(collision: Collision) {

var contact : ContactPoint = collision.contacts[0];
var rot : Quaternion = Quaternion.FromToRotation(Vector3.up, contact.normal);
var pos : Vector3 = contact.point;
Instantiate (particles, pos, rot);
}

any help?