find occurrences of customer numbers in a column and number them 1,2,3,etc

Hi,

I am trying to write a formula that puts a 1 in column H on the first occurrence of a customer code, and a 2 in column H on the second occurrence of the customer code, and a 3 in column H for the third occurrence, etc. Is there an easy way to do this?

Thanks in advance! I've attached an excel doc as an example. The highlighted column is what I would like the end result to be when using a formula.