How to monitor an entire folder tree for new files with PowerShell?

Hey guys,

I am still a PowerShell noob and I have seen this blog post for monitoring a folder for new files.

I was wondering how easy it would be to modify it so that rather than montoring the specified folder, it would monitor the folder and all subfolders for new files?

I have had a bit of a google for WMI queries and 'targets' but I am not finding anything I can understand or use.

Thanks in advance,

AC