You don't need to physically be at a phone to check messages. When you use feature 981, you can press "OTHR". At this point the voicemail, Silicon Sally, will ask you for the Mailbox number, followed by the password, and then press "O.K." You have now logged into that persons mailbox from where you are. You can also setup "Steven's" Extension number as a target attendant from within "ADMIN" on "George's" mailbox. Have George record a greeting that he will not be able to return any calls for a while, and for immediate assistance, to dial "0". This will transfer all callers to Steven.
Hope this helps.