I think communications jitter will make that, well, not such a good idea. If the Logix Controller is a time master, it is a downright bad idea.
If you want to keep the PLC clock synced, it would be better to do it on a much slower interval, one hour, or one day. The RTC really isn't all that inaccurate.
If you are using this for logging purposes to an external database or something, then just pick one time source (HMI OR PLC) and stick to it. Don't mix and match. Or include both timestamps.
If you want to do this for some other reason, it will still have a great deal of random jitter to it, but you can put an On Change event for system\seconds and just write the new value to a PLC connected tag.