Cisco Call Manager 5 external caller's name

Hello,

I've just had CCM 5 installed and can't seem get the incoming external caller's name to display instead of just a number. Have previously used Avaya IP Office and you could have a directory with external names and numbers so when somebody phoned in on their mobile their name would display instead of just a number on the internal phones. Is this possible on the Cisco? I've heard there was an add-in for CCM 4 that would allow it but have found nothing for version 5. Has anybody managed it? Seems like such a simple feature to have!


Any ideas would be much appreciated! Cheers.