How to set calendar permissions in Exchange 2007 using Exchange PowerShell

I am having a very hard time finding this answer yet I know it exists.  In our office we have an Exchange 2007 server running on Windows Server 2008.  Now we previously setup all exchange mailboxes to give a specific user group editor like access to the calendar.  What this means is that every user can open every other users calendar and can create appointments on it at will for whatever user they choose.  I recall doing this through the exchange management shell using some simple command that I specified things like the mailbox where I wanted to apply these permissions and the user group that should have these permissions.  

My questions is how do I do this.  I am nearly positive this command shell command exists but I just do  not know how to find it or what it is.  Any help is grealy appreciated.