Ok, I'm trying to learn how to use threading, but I've run into a problem.  
I'm doing this in VB.Net.  I started out making something pretty simple.  
Just a sort of wrapper for cmd.exe.  I used separate threads to read from
stdin and stderr.  It seemed to be working ok.  Then I added macros to it.  
Here's what's happening.  The sub that runs the commands gets called several
times in a row very quickly.  It's spawns a new cmd.exe process each time,
and a couple of threads to listen for the output.  The problem is that the
commands can take different amounts of time to finish, so the output I get is
all out of order.  I need to make sure that the commands run one at a time,
each one waiting until the previous one is done.  How exactly can I do that?