How to Add a New Event ID Msg to be used by the Event log

[Bob]

Using C# (.net),
I'm writing to the Eventlog using the Following code:

string lsLogname = "Application";
string lsSource = "Heat";

EventLog loEventLog = new EventLog();
loEventLog.Log = lsLogname;
loEventLog.Source = lsSource; // "RimHeat";
loEventLog.WriteEntry("Testing 1-2-3 !",
EventLogEntryType.Error, 1, 6);
loEventLog.Close();

I've added the "Heat" Source under Application in the
registry...

The Event is added to the eventlog & can see it in under
Application & see the erro icon... but when I double click
on it I get the following msg:

The description for Event ID ( 1 ) in Source (
TAGSimulator ) cannot be found. The local computer may not
have the necessary registry information or message DLL
files to display messages from a remote computer. You may
be able to use the /AUXSOURCE= flag to retrieve this
description; see Help and Support for details...

I know that I'm missing the Dll that's attached to
the "EventMessageFile"...

My question is how can I create that dll and what should I
put in it to define a Description to all of my Event Id...

Thanks.
Bob.