Here's the relative Microsoft Tutorial that explain how to use the inside Outlook utility to create .pst backup at scheduled time.
http://office.microsoft.com/it-it/outlook-help/utilizzo-del-componente-aggiuntivo-backup-cartelle-personali-di-microsoft-outlook-HA010075802.aspx
[update 2013.12.12]
Here's another useful link:
http://www.microsoft.com/it-it/download/details.aspx?id=9003
[update 2014.02.25]
http://www.howto-outlook.com/faq/backupaddin.htm