Optimising key strokes for multiple semi-automated file exports (autocad->.stl)

Question

I'm using autocad to slice a very large model into smaller pieces (.stl) for 3d printing. Imagine a 2d road map with all the roads extruded out an inch to created 3d pieces. Since there are many individual .stl files to export (and store) I need to name them. So far this has to be done manually with the pieces named 1-100 for example.

I've refined the process in autocad (using built in functions MULTIPLE and EXPORT) to:

1. MULTIPLE
2. EXPORT
3. save as window appears
4. enter part number: (1:n)
5. enter
6. select part
7. MULTIPLE command returns process to 3.

Ideally I would like to use powershell or something similar to automate the numbering from a for loop and the keystrokes so all I have to do is select each piece iteratively.

Any thoughts?

Note: I am largely self taught and learning autocad/coding on the job. Simple is good!