distutiles extension question

[Eric S. Johansson]

How can I limit when my code run only when it's a build or install 
setup.py command and only after the setup method?

I need to do some processing after setup.py runs and I've been 
successful writing the code to do what I need but the problem is it runs 
every time I run setup.py regardless of the command following.

looking in build.py, I found and internal array called sub_commands and 
it looks like that would be a good place to add my postprocessing but I 
can't figure out quite how to get my code into the right context.

some pointers would be appreciated.  Thanks for your time.

---eric