Hi Dave,
I think that there might be two different solutions to your problem.
1) I've recently started using Ian Donohoe's BGL Exclude kit (excludekit.zip, available here:
http://www.scenery.org/design_utilities_a.htm) which was originally designed for FS98 but works fine with FS9. It is very simple to use - but you do have to be careful where the longitude and latitude coordinates go.
Or:
2) Use the 'exclude' switch that you can insert into the FS9 scenery.cfg, which seems to work in the same kind of way but without the intermediate BGL stage. I haven't used this approach but there's no reason why it shouldn't work. There's a tutorial here (
http://www.planesimulation.com/install1.htm).
Hope that helps.
