I have a spreadsheet which is 4 columns wide and I need to put a count in column 5 for each instance where column 1 is duplicated but column 4 makes the entry unique. I've put the count I need in brackets and the count needs to go upto 10

Example data being:

Fred Smith 01/07/1980 01/01/2005 (1)
Fred Smith 01/07/1980 01/01/2005 (1)
Fred Smith 01/07/1980 02/01/2005 (2)
Bob Jones 01/07/1980 01/01/2005 (1)
Bob Jones 01/07/1980 02/01/2005 (2)

I think it needs to be done with lots of nested if functions!

Can anybody help?

Thanks