Custom AutoCAD routine OjectARX or possible other..

I work with AutoCAD and do quite a bit of development in it useing Autolisp. However I have come accross a situation for which I am unable to create the code that I need.? I think this code may need to be written in ObjectARX within AutoCAD.? However I am open to other solutions if another interface proves to be more suitable for the function. I need a function for the purpose of creating a cutter path.? I do not want the function to create the entire cutter path, basically I would like to write my own routine that will utilize this new function, and create the cutter path from this new information returned. I would like to specify the x, and y coordinates over the top of contoured surfaces, (and/or? a solid if possible)? and have the routine return a point above the surface that is a "minimum" distance from all the selected surfaces (or solid)... In other words picture a ball nose cutter - basically a spherical shape, that has to follow along a path in x, y and z such that it does not? violate any surfaces... It can not just be a specific distance straight up, because as the cutter approaches walls, or if the surface has any incline then there is gouging happening.... I have tried and searched and can not find any good way through lisp. I would be willing to pay someone to do it if its not to large a project. This routine would have to be fast because the routine (from lisp) will need to specifiy the x and y points every 0.001 or to 0.010" and step over a part to be machined in as little as 0.005" wide "rows".? in other words, for a part that is lets say 3" x 6" there could be 1000's or maybe 100,000 points to check very quickly. Perhaps more needs to be done in object arx to attain the speed, that part I do not know.... Thanks for any thoughts you might have. We will have to work on more specific requirements as we go. p.s. Yes I know I can go out and buy CAM systems, this is for a custom application that I must integrate. Thanks in advance for any thoughts on the subject!