Finding port dependants

[Aiza]

The ports make file tree is so very large now a days (21491 ports). 
Doing portsnap to download the complete ports system just to install 3 
ports is massive over kill. I have been doing package installs because 
the resources consumed in disk space (inodes used) and no compile time 
is such a time saver. But there are times when ports have no package or 
the package is not up to date. What I am looking for is a method to find 
the dependents and their dependents of the selected port. Then search 
the package system to determine which have no packages. Install all the 
packages and cvs only the make files for the ports lacking packages. I 
have script to fetch only the make files for the selected port.

So question is, does the ports index which I can download by it's self 
using portsnap contain the info to find all the dependents of a port?

Is there some software I can use to do this?