You don't sound like a "beginner", so check out the Sumproduct() function as
explained very lucidly by Bob Philips on this web page:

http://www.xldynamic.com/source/xld.SUMPRODUCT.html

The XL Help files are completely inept as far as describing the scope of
this function.

Post back with any questions.
--
HTH,

RD

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"Astrofin" wrote in message
...
I use Excel for manipulating and analysing scientific data. I find myself
repeatedly performing similar tasks, and I am sure there must be an easier
way to do this. I would welcome any suggestions.

There are really two distinct problems.

First, datasets of 20-30 columns, 1000s of rows. I want to perform
calculations on multiple subsets within this data. For example a countif
with
criteria from two columns. Currently I sort the data and manually set the
data range of the expressions according to one of the criteria. I'm sure I
am
being slow, but is there an easier way to base this function on multiple
criteria?

Secondly, one of the criteria is month of data collection. This data is
currently stored as a dd/mm/yyyy date data type. Is there an easy way to
make
Excel recognise the month without constructing a complicated function? I
am
using greater and less than functions, but this gets very involved when
dealing with data that covers a number of years. Is there an easy way to
make
Excel recognise the month portion of a date string?

I'm happy to provide more information, I may not have explained this very
well. I would be grateful for any suggestions or insights into how people
approach these sort of issues.

I'm using excel 2003.

Thanks in anticipation.