in allegro 16.0, is there any way to set a higher/lower cost for routing on a particular layer? if so, how?
can this be done with a "Do File"? are there any good tutorials out there on Do Files?
Yes, start PCB Router, Route>Route Editor from within PCB Editor will get the UI running, then Rules>Layer>Costing, hit the help for help. My guess would be that the default layer cost would be "free, as in beer", you can make layers more costly or prohibited to discourage, or prevent, routing.
You can probably do this in a do file, there used to be a MakeDo application that created Do files for the uninitiated, I don't know if the application covered costings.