What you are trying to do is not possible. You can establish only one Bluetooth connection with the cell-phone at the time. You will not be able to make your cell-phone to talk to two N770 simultaneously.

FYI: Only one instance of each Bluetooth service/profile can be active between two devices. However, you can have two different BT services active simultaneously with two different devices. Example: N770 can talk to a GPS receiver (serial port) and to a cell-phone (dial-up-networking) at the same time, but you can not have the GPS receiver talk to call-phone (serial port) and N770 (serial port).

Hope this helps!