I know this is an old post, but I thought I'd share the solution I found...
Excel does not allow you to add a calculated field to row labels. You can add a calculated item, but it does not really help for this problem.
For this particular problem of breaking the date field into month, year, etc., you can use "Grouping." See he
http://office.microsoft.com/en-us/ex...010175903.aspx