What kind of G4?
eMac, iMac, iBook, and Powerbook G4s are much harder than a standard separate monitor.
Although if any of these machines is using a second external display not included with the computer, that can be added like a PowerMac G4 or Mac Mini G4.
These will not work with a MacBook Pro using VNC or Screen Recycler:
http://discussions.apple.com/thread.jspa?threadID=1587927
PowerMac G4 and Mac Mini G4 monitors can be added to a MacBook Pro via a simple A/B or KVM switch once you determine the interface of the monitor and the available interface to the MacBook Pro.
To resolve this issue:
1. What is the monitor in question?
2. Is it built-in to the machine in question, or added separately?
3. If added separately, what is the monitor model and make?
4. What is the display interface of your MacBook Pro?
Message was edited by: a brody