I have a table of data set up as follows:

Customer 31/10/08 30/11/08 31/12/08
abc 20 35 50
def 45 30 24

In a separate sheet I have a summary sheet whichwill show totals as follows:

31/10/2008
Total Port 65

I want the Total port to change according to the date in the cell above i.e.
the total will change to 65 if I put 30/11/08 and 74 if I put 31/12/08.

I don't think this is complicated but at this time of the day its doing my
head in so any help would be appreciated.

Many thanks,

Andrew