I added z depth filter updown boxes to the mappane to allow variable hieght filtering.
http://www.geocities.com/gezs12345/index.htm
I included exe but asalways you should look through code and compile it yourself.
I only touched mapcon and mappane. Added filterzpos filterzneg label4 label5 to mappane. Added filterpos filterneg to mapcon and removed filterrange.
edit stupid geocities link to file is on index page