Hi I hope someone can help me out

I have created a spreadsheet which I want to summarise data from another file.

The source file is a forecast of parts as is laid out as follows

col E row 2 contains the part numer
col G to AP row 3 contains dates ie,02-Feb,09-Feb,02-Mar,06-Apr
col G to AP row 4 cointains the qty of units required

In the summary file I have

col A cointains the part number

I want to enter a formula that will look up the part number in col A and sum
the qty of units required for Feb,March and so on.

I have tried using lookup with sumproduct but I keep getting zero.

Any suggestions would be appreciated, hope you have enough info to go on.