Sumproduct calculation between two workbooks
 

Hi

I am having problems getting a SUMPRODUCT formula to calculate figures
between two workbooks.

One workbook is a marketing campaign register and the other is a sales
register which also records if a sale originated from a marketing campaign
using a campaign reference number.

Basically, I need the marketing register to look in the sales register for
entries that have a matching campaign reference number and add the commission
generated for any matching sales to the 'revenue generated' cell for the
matching campaign in the marketing register.

There are a total of four columns relevant to this calculation across both
workbooks. Two in the marketing register, (say A1) which records a unique
number for each campaign and (A2) which displays the total revenue generated.
The sales register also records the marketing campaign reference for a sale
(B1) and the commission for that sale (B2).

I hope that is clear enough and I would really appreciate any guidance.

Simon