One way

Try, array-entered:
=IF(ISERROR(AVERAGE(IF(('Summary Days'!$D$3:$D$1500="2A")*('Summary
Days'!$K$3:$K$1500=38)*('Summary Days'!$O$3:$O$1500<0),'Summary
Days'!$O$3:$O$1500))),"",AVERAGE(IF(('Summary
Days'!$D$3:$D$1500="2A")*('Summary Days'!$K$3:$K$1500=38)*('Summary
Days'!$O$3:$O$1500<0),'Summary Days'!$O$3:$O$1500)))

(with ranges in your posted formula corrected to be identically sized)
--
Max
Singapore
http://savefile.com/projects/236895
xdemechanik
---
"Rebekah" wrote:
I have multiple columns of data in another sheet and am using this formula
(entered as an array) to provide an average based on conditions, one column
reads "2a", and another reads "38" etc.

i thought that by by entering the IF formula to include "<0", this would
count all the data and return a zero value for a blank or zero value. (I
certainly hope this is making sense to somebody!!!)

=AVERAGE(IF('Summary Days'!$D$3:$D$65536="2A",(IF('Summary
Days'!$K$3:$K$65536=38,(IF('Summary Days'!$O$3:$O$1500<"0",'Summary
Days'!$O$3:$O$1500))))))

This formula works if in all columns there is a value above zero, but
returns "#DIV/0!" if not. This would be ok if my table wasn't presenting
data for a fixed period....
Please help!!!