The Select a Region page, which lets you select the line or region that you wish to find the latest change.  When focus is in the central Text box, you may use the following keyboard shortcuts:

The Results page, which will query the server for the latest version of the file in which any of the lines in the selected region changed.  This page will list the user, version number, date and comment for the transaction which changed the lines.  You may click the Diff Against Previous button to load the diff tool to display the changes which were made in the transaction.  If you click the Next button, you will be taken to the Select a Region page populated with the version before the change was made.  This allows you to continue to search for the ways in which this line changed throughout history.