sequential numbering duplicate data

I have a worksheet (brief copy attached) that has duplicate data "h" that I want to assign a sequential number to the left column of. 1st "h" 1, 2nd "h" 2 and so on to be used for a vlookup function in another sheet.This sheet is constantly growing with an copy/insert macro I created so I need it to expand as other entries "h" are made. Here is a before and after example.