Excel Gurus,

I need help, I am trying to find a formula to indicate the last duplicated string in a column by placing a 1 next to it, please see below:


A B C D
Date Name Laps Final Laps Recorded Indicator
5-4 Dan 23
5-6 Billy 21
5-3 Mike 26
5-8 Billy 22 *
5-3 Dan 28 *
5-10 Mike 26 *


Based on this table above, I want to find the last duplicated name in column B, and put a one by it in column D so it should look like this:
(in my spreadsheet there are empty rows between data because of the way it is imported, so the formula would need to account for that)
A B C D
Date Name Laps Final Laps Recorded Indicator
5-4 Dan 23
5-6 Billy 21
5-3 Mike 26
5-8 Billy 22 1
5-3 Dan 28 1
5-10 Mike 26 1


I cannot seem to figure it out, any help would be appreciated!