Make child on the edge of the parent circle while scaling

Hii all..

I have come across to some different situation. I have one circle sprite and i am rotating circle continuously while rotating i want make circle smaller and larger. I have one object on the edge of the circle i have made that object as child of the circle.

Now my problem is how to make this child object to stay at the edge while i scale circle sprite . I s this possible ?

Thanks.