Change object on button down precisely at an object - unity3d

Question

I have a target object (cube), and a fake mouse that I created from an object (sphere) to be controlled by gamepad joystick. I want to bring out another object (let say; sphere), when I push the gamepad button and precisely hit the target object (cube).
Before, I have tried with a mouse click, and it succeeds, but when I controlled the fake mouse with a joystick, when I press the button even outside the target (cube) it still brings out another object. Here is the code, if anybody can help me to revise it. Thanks
function Start () {}
function Update () {
if (Input.GetButtonDown ("Fire1"))
{
var Cube = GameObject.FindGameObjectsWithTag ("Cube");
if (Cube[0].GetComponent(MeshRenderer).enabled){
var Circle1 = GameObject.FindGameObjectsWithTag ("Circle1");
Circle1[0].GetComponent(MeshRenderer).enabled = true;
Circle1[0].GetComponent(MeshRenderer).material.color = color.red;
}
}
}

Answer 1

[solved]
Thanks to EmreE and Draco18s for replying my question. I have solved it, I made a collision trigger indeed.
Here is my code after several trials.
if (Input.GetButtonDown ("Fire1") && isCollide)
{
var Cube = GameObject.FindGameObjectsWithTag ("Cube");
if (Cube[0].GetComponent(MeshRenderer).enabled){
var Circle1 = GameObject.FindGameObjectsWithTag ("Circle1");
Circle1[0].GetComponent(MeshRenderer).enabled = true;
Circle1[0].GetComponent(MeshRenderer).material.color = Color.red;
Debug.Log("Muncul");
}
}
function OnTriggerEnter (col : Collider)
{
Debug.Log(isCollide);
if(col.gameObject.name == "Mouse3DSphere")
{
isCollide = true;
}
}
function OnTriggerExit (col : Collider)
{
Debug.Log(isCollide);
if(col.gameObject.name == "Mouse3DSphere")
{
isCollide = false;
}
}