Summing Range Max

[#1]

I'm trying to sum the greatest number of hours for every day.

i.e. I want the sum of the bolded numbers below: 19

Date	Hours
1/2/2011	2
1/2/2011	3
1/2/2011	4
1/3/2011	2
1/3/2011	4
1/3/2011	9
1/3/2011	2
1/4/2011	3
1/4/2011	6

I can't sum(max(hours), any other ideas?

[#2]

sum(aggr(max(hours),Date))