Dial by Name looks at Unity Express users (assuming you're using a CUE script to accomplish dial by name). So, as long as you didn't setup a CUE voicemail box, John Doe, extension 104 should be excluded. Another option is to setup a shared line between the two phones so that they are both extension 100.
Configure Multicast Paging on the Cisco IP Phone 7800 Series or 8800 Series Multiplatform Phone
The Cisco IP Phone 7800 and 8800 Series Multiplatform Phones provide voice communication over an Internet Protocol (IP) network...
Add Call Park on a Cisco 7800 or 8800 Series Multiplatform Phone Key Expansion Module
Call park allows the user of the phone to put an incoming call on hold so that the call can be retrieved on another phone. A call is park...