Thanks, but unfortunately I am looking to have a column of check-boxes and have a neighboring column show when each is checked. Your idea would work if we had an option on NOW() call to not update once it is set. For a moment I thought that perhaps the pull-down "Show Function as Text" would do that, but it does not 'freeze' the value.
One way to do what I want manually is, right after checking the "check-box-cell" so the "time-cell" is now showing time, to then immediately copy the time-cell (with command-C) and then paste it into itself with "Command-Shift-V". This also turns the time-cell to text so it will not provide the function anymore if the check-box is unchecked.