using fs.OpenTextFile without .TXT

[jimib]

I need to write to a textfile and name it with an extension other than ".txt" (an archive file) . For example: myfile.123
I can't seem to get around the file system object adding ".txt" so my filename becomes myfile_123.txt
Do I need to write it another way or is there some way to do this with fso, which I'm comfortable with?
My (nonworking) code:

Conn = fs.OpenTextFile("c:/inetpub/wwwroot/app/files/f.123", 2, True)
for each obj in s 
  Conn.WriteLine( obj & "'" )
next obj
Conn.Close()