Write a program LISP

We need to write a program for work for AutoCAD. In the drawing, we have two surfaces (each surface is created by objects 3D faces). 3d faces of each surface are in their own layer. it is necessary to calculate the volume between these surfaces (Cut\Fill). Program description: The user starts the program, It is proposed to choose two surfaces between which the calculation of the volume,the program suggests choosing the boundary in which the calculation will be made (closed polyline). If the boundary is not selected, the calculation is made over the entire common area where the surfaces intersect. The program calculates the volume and outputs the result to .dcl. The user is also invited to insert the result of the calculation in the drawing. In the attachment, a drawing with an example of what we have.