Okay...  That gives me the basics...  I guess the peice that I'm missing is
how to implement a performance counter for an external app.  Here's the
situation:

SQL Server does not expose a counter to report the number of data access
blocks currently on the system.  But it's something that can be queried from
the master tables.

Obviously I can't add the counter to SQL Server itself.  I just want to
create a new counter that exposes some SQL Server stats through perfmon.

So if I want to create a perfmon counter to present that, do I have to
create a service that runs in the background and updates the counter on a
regular basis?

Thanks.

Jerry