CISCO SYSTEMS SMB UC540 2-digit to a 3-digit extension conversion

We currently have a UC540 setup using 2-digit extensions. At the time I didn't know this was going to be an issue if we wanted to use another UC540 in a mutli-site configuration as you need to be running with 3-digit extensions. I understand you have to do a Factory Reset to make the current UC540 using 2-digit into a 3-digit one. But we don't want to factory reset the uc540. We have had this system about 18 months and I've done everything with the CCA. I understand you may have to do these changes (if possible at all) via CLI which I don't have a huge problem with (if you can't do it via CCA as I can't see how) You may try to change the extensions in the CUE from 2 to 3 digits. in the CUE via CLI If you can do this please bid.