For all of the following, you should have two tables linked in a relationship. Individuals would have one record for each person that might log in or out. Log, would have one record for each time a person logs in/out. They'd be linked in a relationship like this:
Individuals::__pkIndividualID = Log::_fkIndividualID
For an explanation of the notation that I am using, see the first post of: Common Forum Relationship and Field Notations Explained
You'd then use a layout based on Individuals to display the most recent info from Log for each individual.
The Last Function can return the last related record where the referenced field is not empty. Thus, you can set up a calculation field that returns data from the last related record, but note the requirement that the field not be empty.
You can specify a sort order in the relationship that makes the most recently logged record for any given individual the first related record. You might sort on a serial number field or a timestamp field in descending order.
You can set up a portal to Log on the individuals layout. This can be a one row portal if you wish to only see one log entry for each person. Specify the same sort order I mentioned for Option 2, but as part of the portal setup instead of the relationship.