Circle packing inside curve

Hi everyone! 

With a lot of help, I wrote a VB component  to create a tree of circle gravitating around a center point. 
Now I'd like to contain them inside a curve that we can input but as i am new to VB i don't really know how to do it. 
Can someone please help me to write a piece of VB script so that the circles don't go out of the input curve? 

Thanks.