Pipe networks, corridor and earthwork calculating, any help ?

[cyberflow]

Hi there ...

I'm working on a projet and i need to calculate the rock from the geologist survey VS the normal earth on it.

Until now things are simple.

But where it gets twisted it that i need to calculate the cut from the projected network pipes.

I did a quick sketch so we could all understand what i'm trying to say : 

Id like to generate a surface that will generate the cut surface for the projected network (Sanitary, rain, water) with a given Y offset (for the material to be put before puting the pipes).

Is it possible to give multiple points of controls to an assembly ?

[cyberflow]

I guess my questions is too complicated or not enough specific ?


Basicly id like to know if i can give multiple points of controls (in this case 3 pipes) for my assembly ?