Try this array formula** :

=AVERAGE(IF((ISNUMBER(A1:A31))*(F1:F31<0),F1:F31) )

** array formulas need to be entered using the key combination of
CTRL,SHIFT,ENTER (not just ENTER). Hold down both the CTRL key and the SHIFT
key then hit ENTER.

--
Biff
Microsoft Excel MVP


"Seth.Schwarzkopf" wrote in
message ...
i have a sheet that collects data by the date (1/1/09,1/2/09....) and then
comes up with the differences in usage from day to day. in column "F" i
have
the data i want to average for the month but i cant just do
=Average(F1:F31)
because in this column i have it totaling for the week. how can i average
the month but skip the cells that hold the weekly total and not average
any
cell that has a zero in it?
it kind of looks like this..
A F
1/1/09 .001
1/2/09 0
1/3/09 .0058
Total .0068
1/4/09 .012
The weekly totals fall every saturday not every 7th day of the month
please
help been racking my brain for a few days thanks in advance