EVE Technology Lab

I'm very new when it comes to xml and APIs and all that stuff, but most of my stuff is working as intended in my market spreadsheet. I recently discovered this: http://eve-marketdata.com/developers/item_history2.php

If I'm understanding it correctly, one of the values that API returns is "volume" (# of units sold) in the region you specify and for the time period and typeID you specify. Now, for the market spread in my Excel spreadsheet I've used "//buy/max" and "//sell/min" in the part of the formula where it asks for a value for "xpath". What is this xpath for the volume value in the eve-marketdata API?

I think this is pretty much public knowledge (and fairly basic) so I don't think anybody's giving any trade secrets away. I can give a small ISK reward for someone who can help me with this if that's required. Any help would be appreciated, not only because this might help me with EVE but also because I want to learn more about this aspect in Excel.