Use powershell to move exchange folder contents from one user to another?

I need some help getting started with an Exchange 2007 management shell command that does the following:

Move the contents of the "Junk E-mail" folder for USER1 to the "Junk E-mail" folder for USER2.

I intend to do this for all users on the system so if there's a good wildcard to use in place of USER1 that'd be handy.  TIA!