extrude surface till surface intersection

Hi,

I am currently having a problem extruding a group of circles in a z distance till a surface. I need the maximum domain of the distance to be extruded to be the distance from the circle's center till the surface. 

I am sending a few images of what I am trying to accomplish. 

The grasshopper that I am sending has a lot of things but the final few components are the ones that you will need. 

Thanks for all the help :)