Do you mean that Jabber is 'connected' to your desk phone, but you'd like to do a video call by using the webcam on your PC?
If that is what you mean then yes you can do this.
What you need to do:
1. Ensure the PC is plugged into the back of the handset (PC port).
2. Installed Jabber Video Services interface (previous Cisco Media Services). It is available from the Jabber download page.
3. Enable Video on the phone device in CUCM.
That should do it. Check out http://www.cisco.com/c/en/us/support/docs/unified-communications/jabber-windows/116472-problemsolution-product-00.html