I have 3 columns of data.
The first contain a list of start dates, the second a list of end dates, and
the third a list of numbers.
I want to create a table as follows:
I enter my one start date. This only looks at the rows where this start date
corresponds with my start date. I then use sumif to get the sum amounts on
every end date for that particular start date. I can do the sumif bit, howver
i only want it to sumif the second and third columns where the start dates
match my original start date.

Can you help?

e.g
Start Date End Date Number
June August 10
June September 12
June August 4
August September 5

I want to achieve the following
Start Date End Dates July August September
June 14 12
I can sumif on columns 2 and 3, but only want to do this if the first column
has the correct value as i the example above
Hope this is clear