Maybe something like this.

Code:
$filehandle = FreeFileHandle()
If Open($filehandle,"C:\TrackitAudit.id",2)=0
   While @Error=0
      $line = ReadLine($filehandle)
      If InStr($line,"LASTRUN=")
         $lastrunmonth = SubStr($line,13,2)
         If $lastrunmonth <> SubSTR(@DATE,6,2)
            $null = WriteValue ("HKCU\Software\Microsoft\Windows\CurrentVersion\RunOnce","TrackitAudit","\\na\netlogon\pcaudit\audit32.exe","REG_SZ")
         Endif
      Endif
   Loop
Else
   $null = WriteValue ("HKCU\Software\Microsoft\Windows\CurrentVersion\RunOnce","TrackitAudit","\\na\netlogon\pcaudit\audit32.exe","REG_SZ")
Endif


Still doubt that the id file is being modified by the script in anyway. But this method should work. Doing pretty much the same thing as before, except its getting the month from the data in the file instead of the modify time of the file.