Hi Angie,

Lots of good questions there. They all take a bit of explaining so I'll point you to two articles to read and then, once you've read them, we can discuss any outstanding questions you have?

http://www.xldynamic.com/source/xld.SUMPRODUCT.html

http://www.xtremevbtalk.com/showthread.php?t=296012 (particularly posts #5 and #7)

Let us know how you get on...