select you data and do Data=Pivot Table report

Make the data/time your row filed and you stream values the data field. If
you have xl2000 or later, this is done on the last screen of the wizard by
selecting the layout button. When you drag the data field to the data
area, double click on it and select average.

when the table is created, the right click on the row field and group on
day.

This should give you your daily average.

I assume you date and time are in the same cell. If you have them in
separate columns, insert a dummy column and do

=A2+B2
in C2

format it as date and time using the custom format, then drag fill down the
column.

Debra Dalgleish has some information on creating pivot tables at her site.
http://www.contextures.com/tiptech.html

--

Regards,
Tom Ogilvy

"jen" wrote in message
om...
hi-
i am using Microsoft ME Exel, Pentium III, 127 MB RAM. i have many
years worth of 10 minute streamflow data and need to compress it into
daily averages.

the data is set up like this
1/1/03 00:10 .56
1/1/03 00:20 .89
1/1/03 00:30 .91
etc, for a whole year, in three columns

any help to save me from endless hours of averaging, cutting, copying
and pasting is GREATLY appreciated!