Deskproto CAM machine relief without sidewalls to try and make a raised relief

[chris]

I am using Deskproto CAM to try and make a raised relief map. When I generate toolpaths I notice that it automatically creates the vertical sidewalls of the model, when I want it to simply machine the top surface relief and leave the sidewalls alone.

Any ideas how I would instruct a CAM program to leave the sidewalls alone?

Here is a little screen shot to illustrate. Thanks in advance. Chris