How can you plot data that is less than daily? I typically create charts of
data that has hourly or even 15 minute time steps. Excel will sum all the
values for the day and just plot daily data, or monthly, or yearly.

Sample Data:
A B C
Date Time Flow(mgd) Rain(in)
2/13/2007 1:00 1.2 0
2/13/2007 2:00 1.3 0.1
2/13/2007 3:00 1.5 0.2
2/13/2007 4:00 1.1 0