I have a spreadsheet containing sales by customer and material by week. On a
seperate spreadsheet I have the dates during which each customer and material
were on promotion. Each customer has a number of different promotions across
the year for the same material so I was planning to use a sum if to specify
my date range and an embedded vlookup to specify the specific row I wanted to
add the sales in. Simplified version of the 2 sheets are below

Sheet 1 (promo details)

Promotion Customer Material Buying from Buying to
Test 1 Cust 1 SKU1 01/01/2009 17/01/2009
Test 2 Cust 2 SKU2 02/02/2009 02/03/2009
Test 3 Cust 3 SKU3 02/02/2009 02/03/2009

Sheet 2 (sales data)

Week
Customer Material 01/01 08/01 15/01 22/01 29/01 05/02
Cust 1 SKU1 5 18 13 2 2
Cust 1 SKU2 5 8 9
Cust 1 SKU3 4 3 3 3 2 18
Cust 2 SKU1 5 18 13 2 2
Cust 2 SKU2 5 8 9
Cust 2 SKU3 4 3 3 3 2 18
Cust 3 SKU1 5 18 13 2 2
Cust 3 SKU2 5 8 9
Cust 3 SKU3 4 3 3 3 2 18

I cannot figure out how to make the 2 sheets talk to each other. Any ideas?