Unfortunately this is not possible. Pickup groups work by individually assigning your extensions to a pre-configured pickup group.

For example, if your extension 3000 has been assigned to the pickup group 8888, as has 2001, then you simply press the pickup softkey to retrieve the call.

Below are the pickup group options:-

Call pickup-Allows users to pick up incoming calls within their own group. Cisco Unified Communications Manager automatically dials the appropriate call pickup group number when the user activates this feature from a Cisco Unified IP Phone. Use the softkey, PickUp, for this type of call pickup.

Group call pickup-Allows users to pick up incoming calls in another group. User must dial the appropriate call pickup group number when activating this feature from a Cisco Unified IP Phone. Use the softkey, GPickUp, for this type of call pickup.

Other group call pickup-Allows users to pick up incoming calls in a group that is associated with their own group. The Cisco Unified Communications Manager automatically searches for the incoming call in the associated groups to make the call connection when the user activates this feature from a Cisco Unified IP Phone. Use the softkey, oPickup, for this type of call pickup.

When more than one associated group exists, the priority of answering calls for the associated group goes from the first associated group to the last associated group. For example, groups A, B, and C associate with group X, and the priority of answering calls goes to group A, B, and then C. First, group X picks up incoming call in group A, though a call may have come in earlier in group C than the incoming call in group A.

The above is taken from the following document URL it discusses these options, also a feature you may be interested in is the auto call pickup:-

http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/admin/6_0_1/ccmfeat/fscpickg.html#wp1072259

HTH

Allan.