=SUMPRODUCT((x1:x999="category")*(y1:y999="style") *(z1:z999="size")*(w1:w999)

assume 999 lines and that "category" is replaced by your criteria for
category, etc.
these criteria can also be references to cells

http://www.xldynamic.com/source/xld.SUMPRODUCT.html for more info


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MDubbelboer
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