I would really appreciate a bit of help in calculating a formula.

I have a spreadsheet which is summarising data from another file.

The source file for the data is set out as below

col E row 2 contains the Part number
col G to AP row 3 contains dates,ie, 02-Feb,09-Feb,06-Mar,19-Apr
col G to AP row 4 contains number of units required

The next Part number begins on col E row 9
col G to AP row 10 contains dates,ie, 02-Feb,09-Feb,06-Mar,19-Apr
col G to AP row 11 contains number of units required

and so on.

My summary file has the Part number in col A

In col D I want a formula to look up the part number in col A and sum the
qty of units required for Feb,March etc from the source file.

I have tried vlookup and sumproduct but I cant get it to work, please help
as it's doing me head in, been trying for hours.

Thanks
Winnie