My experience with previous versions of BackupExec didn't expose comparative reporting like that (but maybe it's been added in the later versions). We used to use TreeSize Pro from a scheduled task to generate XLS files on a periodic basis, and then used Excel conditional formatting to highlight differences (new directories, directories that changed by more than "x" MB or "y" percent) between two XLS snapshots.
It was a bit "home grown", but it worked for us.