Help with Dynamic Prior Period using Relative Date slicer (Sample Data)

I have a simple dataset but need help with how to create a measure for a dynamic period over period conversion rate using a relative date slicer.

For example, a user enters 7 days in the relative date slicer. I need a measure for the prior period conversion rate  = (Inbound_Calls/Page_Views) for the period of 7 days prior (days 8 - 14). If the users were to enter 10 days in the relative date slicer I would need to show the prior period conversion rate for the period of 10 days prior (days 11 - 20).

SAMPLE DATA