Hi Joe,
The first option that comes to my mind would be to make multiple separate 2D milling operations that cut at the different depths, and then using a custom modified G-code post specifically for the project file that includes a pause command block between operations. You would need to include the pause command in either the tool change block, one of the the spindle command blocks, or one of the coolant command blocks. It would basically be a bit of a hack where you're just including the pause command inside one of the command blocks that are issued on a per-operation basis. Then with separate operations each cutting a different level, and exporting the G-code using such a custom post as described - with operations combined, you would have the desired result where each cut level would include a stop to let you push a button and tell it to continue.
The second option would be creating each cut depth as a separate option and exporting them as separate G-code files, which would require opening each one to run it for each cut level.
That's the best I can come up with at the moment - but it does give me an idea to include some new functionality in the G-code post-processor format that allows for different commands to occur at different times, such as per-operation, per-toolchange, or every N operations, etc.. I'll have to think about that though and see what I come up with :]
- Charlie