Get instances of rows in excel for a particular group

Question

I have a dataset containing a list of check numbers.

Check
111
111
111
222
222

I am trying to have a new column in my dataset that would give me the 1st, 2nd, ....nth instance for every check. The output would like something as below,

Check	Instance
111	1
111	2
111	3
222	1
222	2

Answer 1

You can use the COUNTIF function with an expanding range to generate a rolling count for a particular instance that appears in a range of cells.

=COUNTIF(A$2:A2,A2)