Figuring counts based on time frame.

So I figured this would be simple but the answer has alluded me.   I have a table that holds call informaiton.   One column is for the Telephone Number of the caller, one is the Queue the caller called into, and one is the Date the call took place.   What I'm needing to do is find a way to count how many times a customer called back in within a three week period.  So essentially if a customer had 2 or more calls happen within a three week period count it, otherwise exclude it.  I haven't figured out how to accurately count only calls that have happend twice or more.  I finally figured out how to count calls between dates but not sure if this is the correct path since this will count all calls instead of just the multiple onces.  (BeginDate and EndDate are just datediff 3 weeks from all date in either direction)

TestingMeasure:=CALCULATE(COUNTROWS(F_QUEUE_CALL_DETAIL),FILTER(F_QUEUE_CALL_DETAIL, ([BeginDate] <= LASTDATE(D_DATE[Date])
&& [EndDate]>= FIRSTDATE(D_DATE[Date]))))