I had created a reply but not sure whether it will get posted...

Basically you need to find the networkdays for a given project and month
between MAX(Project Start Date, First day of the Month) and MIN(Project End
Date, Last day of the month) and then sum across projects for that month and
repeat for all months.
You may use helper columns or have a one big formula...
For last day of the month use
=DATE(YEAR(A1),MONTH(A1)+1,0) for the date in A1 and
=DATE(YEAR(A1),MONTH(A1),1) for the first day of the month

"GavinD" wrote:

Im trying to summarise the number of NETWORKDAYS spent on projects by month.
The data I have is as follows: (dates are in UK format)

A B C
1 Project Name Start Finish
2 Project One 22/02/2008 13/03/2008
3 Project Two 22/02/2008 06/03/2008
4 Project Three 25/02/2008 11/03/2008
5 Project Four 25/04/2008 12/05/2008
6 Project Five 09/05/2008 06/06/2008
7 Project Six 13/05/2008 27/05/2008

The result I am looking for should look like this:

9 Month Number of Days
10 January 2008 0
11 February 2008 17
12 March 2008 20
13 April 2008 4
14 May 2008 35
15 June 2008 22

I have tried various combinations of arrays using SUM, SUMIF etc but cannot
find a solution. Any advice would be appreciated.

Many thanks in advance.