Formula needed to return an array of items based on lookup value in another column

I have a sheet with inventory data

A - stock code
B - usage
C - stock on hand
D - item name

Usage data is shown by month so there could be 0 - 12 rows for each stock code. Stock on hand is the current stock available (same for all rows of a single stock code).

I need to find all cases where total usage for the year is 0, but we have stock on hand. That means for each stock code, I need to find all the rows where it appears and return a sum of usage for all rows. I would then like to display:

stock code, total usage for year, stock on hand, item name

I'm not sure what combination of functions can help me with this. VLOOKUP only returns the first instance of the stock code and usage. I need a function that will return an array of numbers (all usage values) or something to that effect. How can this be done?

Thanks,
Mike

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Have you taken a look at the SUMIF() function...

it sums values in one column based on criteria in another column...

e.g. =Sumif(A1:A100,"X",B1:B100) this would sum values in B1:B100 where A1:A100 contains an "X"

How about Pivot Table?

http://peltiertech.com/Excel/Pivots/pivotstart.htm