count duplicate rows and add the count to the last column

I have the following data,
wo      name      opn      hrs      labor      count
123      john      20      1      L      2
123      john      20      2      L      2
123      mario      30      3      S      1
123      sue      40      4      S      1
123      jose      50      5      S      1
I need to count the number of duplicate rows base on wo,opn and labor and put the results on the count column. In the sample above record 1 and 2 are the same therefore the count column is 2 on both rows. the number of records might vary depending on the data dump. Appreciate any help on this. thanksStart Free Trial