By using the 'Embedded Scripts' feature and the 'Application Scheduler' feature you can create a script that will write the disk defrag information to your local event logs on a regular basis.
1). Create the following embedded script:
defrag.exe %Systemdrive% -a -v
(This should have a BAT or CMD extension so it is run with the command interpreter).
2). Use the 'Application Scheduler' feature to run your embedded script on a regular basis to write the results of your script to the event logs.
Further information on both of these features can be found at the following URLs: