How to use dictionary method instead the function Countif in VBA?

[Gabrielle9]

Hi! I want to use vba dictionary method because i have over 200k rows which takes a lot of time to run. I found that using dictionary method would be faster than Worksheet countif function, but i could not find somethig to convert my formula to something that will return each appearence of the duplicate value

My excel formula:
=If(countif($N$2:$B$200122,N2)>1,"Duplicate value", " ")

=If(countif($N$2:$B$200122,N3)>1,"Duplicate value", " ")
..............
If(countif($N$2:$B$200122,N200122)>1,"Duplicate value", " ")

Vba code:

Lastrow= cells(rows.count,2).end(xlUp).row
For n=2 to lastrow
If application.countif(range("N2:N") & last row), Range ("N" & n)) > 1 then
Range("O" & n).Value = true
Else

 

[Gabrielle9]

Range("O" & n).Value = false
End if
Next n
This is the my complete code. Is posible to use dictionary to have the same result as when i use countif function?
Thanks!