Automate Sharepoint Backup Full and Differential

Hi,

i have created to seperate script to automate sharepoint full and differential back. Full backup on bi-monthly and differtial daily.

Backup location is e:\sharepoint_backup.

When full backup run it creates XML file and folder like spbr0000 and spbrtoc.xml. i want to rename spbr0000 like Full-spbr0000 and when differential run Diff-spbr00001.  Plus want to delete backup older than 3 days. i am using / referring following script 

http://blogs.technet.com/b/schnood/archive/2011/04/19/simple-sharepoint-farm-backup.aspx 

Please guide me how can i rename backup folder.

thanks.

iffi