Multiplying and summing attributes that appear in a list

Hi,
maybe someone can help me out with my problem.
I have a list, 50-150 rows long. The list is being filled regulary, and sometimes the word "Box" will pop up, followed by its width, hight and length, like this:
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Box
width 10
hight 20
length 30
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What I want to achieve is to sum the volumes of ALL boxes that pop up in the list.
Im thinking i could do this by locating the first "box" by searching from the top, multiplying the attributes with the shift or dislocate function or whatever its called in english, and search for the next "box" from there. However this would meen a very big formula...Could this be a task for Mr. Sumproduct perhaps...?
It will pop up 6-7 times.

Thanks
/Johan

Perfect
Thanks alot!