Conditional Outlook Event Date

Hello,

I am trying to create a new event in my Outlook calendar that will set the date of the event based on a condition:

I want the even to occur on the 15th and last day of every month.  But if the 15th or last day is on a weekend, I want the event to occur on the Friday before.

I am pretty new to Outlook and creating events in my calendar so I apologize if this is a relatively simple task that I am over looking.  I haven't been able to find much for this online anywhere, so either links or answers will be very helpful!

Thanks!