[ODE] Collision detection without forces

[gable78 at aliceposta.it]

Hi, 
I'm a newbie with ODE. 
My problem is:
I'm in need to know information (normal,depth....) about the contact points 
between two geoms without generating any kind of force. I try to explain 
better...i have to touch a cube with a little sphere e so i want to know 
collision point, depth and normal but no force must be applied to the cube.
Do someone have an idea?

Thanks for your help!
Gabriele