To my knowledge, that is out of the box not possible. You should be able to get this information from the samba-log, but that is much to sift through. Something like this could work:
cat /var/log/samba/log.* |grep -A 1 make_connection_snum > logons.txt
pdbedit is AFAIR also able to display logon/logoff times (maybe you can build a script from this):
pdbedit -L -v -u <username>
There should be third party tools, that also give you a report, that may be more effective.