PocketMax has a freeware software that allows your phone to redial a busy phone number at regular schedules via a popup notification. You can choose to rdial every X minutes as well as set the number of attempts. The software runs in the system tray and allows you to Activate/ Deactivate via the tray icon as well as shows the current status through visual notifications.

Link- http://www.pocketmax.net/redial.html
Download Link-http://www.pocketmax.net/_d\redial_setup.exe