Hi
I have a query which I hope that you can help me with.
I have a formula which counts how many duplicates there are in a list of ID’s. (below)
=IF(COUNTIF(F$2:F2,F2)>1,"Duplicate # "&COUNTIF(F$2:F2,F:F),IF(AND(COUNTIF(F:F,F2)>1,COUNTIF(F$2:F2,F2)=1),"Duplicate # 1",""))
What I need is another formula which basically finds the last duplicate and then subtracts the difference in dates from the first duplicate and the last duplicate to give the number of days.
The formula I am using to find the last duplicate is: 
=IF(AND(COUNTIF(F$2:F2,F2)=COUNTIF(F:F,F2),COUNTIF(F:F,F2)>1),"Last Duplicate","")
The dates are in Column B.
Is this possible?
I would really appreciate some help with this.

Many Thanks in advance.