I need to find out how many people are mis-typing a web address when
typing a search directly into the address bar of a browser such as
Microsoft Explorer or Netscape.

For instance, I want to know how many people are typing www.msncb.com
instead of www.msnbc.com

I am looking for a counter of addresses that are directly typed, not
addresses that are being searched on an engine such as Google. What is
the web address where such a counter exists (if one exists at all)?

That kind of counter does not exist. It's simply impossible to control
what every user in the world is typing. It would be possible to write
a program that would do that, but every user would have to install it
in order to be tracked.