[vtkusers] Moving an actor along a surface with surfacenormal orientation

[Michael Kozel]

Hi everybody,
I am using VTK 5 and VS 2005 (VS8). I try to move an vtkActor out of an vtkCylinderSource along an Actor surface of  polygonalData.
I tried to pick the Cell and/or point with vtkCellPicker or vtkPointPicker, but it was very slow. Then I tried to get the normal  of the picked cell previously computed with vtkPolyDataNormals() by using GetDataSet()->GetCellData()->GetNormals()->GetTuple(CellID).
I also hedghoged the normals to see if it is the same direction and it wasn't. 
What is wrong?
How can I move the cylinderActor along the surface with the direction of the surfacenormals under the currentEventposition of the Renderer?
I am an absolute newbie. I hope you understood my poor English and may help me.
The surface is a skull where I should put trajectory-points later on to cut the bone.

Thank you for your answer to come.
Michael