call waiting pickup...

Hi all. Can somebody help. System is option 11c and i made a call wait
key on five M3904 sets and on some analog sets. Now user wants that if
he is busy on call and 2nd call comes on call wait key then it should
be pick by some code by other extension like we made pick a call of
ringing extension(by pickup group code).is that possible??? or any
trick to do that???
Or simply can we pick call waiting call by any FFC code.
thanx and regards

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