Surface Manipulation

I am looking to take a flat surface and create a depression into that surface along a curve. I would like to be able to break the curve into segments and move along the path in intervals with the ability to change the depression amount. To this point I have been able to extrude the surface to a point but this does not create a smooth depression. Attached is Grasshopper file, Rhino File, and Animation of my work up to this point.