Sync Outlook for Mac Calendar with iPhone

Hi All, I have been desperately trying to sort this issue out.

I need to sync my Outlook for Mac Calendar (Outlook for Mac 2011) with my iPhone 5. I am using Mac OS X Yosemite. I have tried Sync Services to iCal and then selecting Calendar in iTunes and all I get is the calendar entries from the phone coming into iCal.

I'm happy to use a third party app/software if it will work. Please help.