Hi Juan,

Unfortunately this feature is not available until the CCM 5.x train. The BLF listed in CCM 4.2 relates only to the Directed Call Park feature not the ability to monitor a Directory Number associated with a user. Have a look.

Configure directed call park numbers in the Cisco Unified CallManager Directed Call Park Configuration window. Configured directed call park numbers exist cluster wide. You can configure phones that support the directed call park Busy Lamp Field (BLF) to monitor the busy/idle status of specific directed call park numbers. Users can also use the BLF to speed dial a directed call park number.

From this good doc;

http://www.cisco.com/en/US/products/sw/voicesw/ps556/products_administration_guide_chapter09186a008070e4b5.html

In CCM 5.X you are referring to this functionality;

A Phone Monitors a BLF/SpeedDial.

After an administrator configures the presence feature and the BLF/SpeedDial buttons, a user can immediately begin to monitor the real-time status of a presence entity.

From this doc;

http://www.cisco.com/en/US/products/sw/voicesw/ps556/products_administration_guide_chapter09186a008062b705.html#wp1134881

In CCM 4.2(3) you would still only be able to add a "Shared Line" appearance of the specified DN to the 7914 to monitor activity.

Hope this helps!

Rob