=AVERAGE(IF((HOUR(F8:F28)=10)*(HOUR(F8:F28)11),G 8:G28))
An array formula that must be entered using ctrl+shift+enter
--
Don Guillett
Microsoft MVP Excel
SalesAid Software

"Chris26" wrote in message
...
Hi
I have the following data
Col-A Col-B
1/10/2009 10:20 0.006
1/10/2009 10:22 0.007
1/10/2009 10:24 0.006
.......
1/06/2010 15:00 0.015

etc
What I would like to be able to do, is to calculate the average of the
vaules in Col B only between certain time periods i.e. 2am and 4am for
each
day in the data set

Any help appreciated.
Many Thanks
Chris