A spreadsheet contains 3 columns: "Item", "Week no." and "Year".

F.ex.:

A B C
1 Item Week Year
2 101 32 2006
3 101 32 2006
4 101 32 2006
5 101 32 2007
6 101 32 2007
7 102 32 2006
8 102 33 2006

In another cell I wish to count how many of the different Items (f.ex. 101)
are listed in f.ex. week 32 AND year 2006, but only for these. In the above
case the result should be 3.

It seems simple, but I just can not figure it out. Can anybody give me the
formular for this? Thanks.