InfoPath Dev

Ok, after 5 hours trying to solve this, I give up!!

 This is what I am trying to do:

I am creating an Infopath 2010 form to request printouts in a SharePoint Library. Since i have color and blak/white pages, I need to sum the total of color pages separately from the total of black and white pages (like a sumproduct in Excel).

My formula would calculate:

Total Color = Sum ( if (Color = "Color" , No_Pages * Times)

Total B/W    = Sum ( if (Color =  "B/W" , No_Pages * Times)

 This is how it looks in XPad:

sum(xdMath:Eval(../my:group8[../my:group8/my:Color = "B/W"], "../my:group8/my:No_Pages * ../my:group8/my:Times"))

Obviously I am making a mistake since the form doesn't calculate the values as I expected. Any suggestions?

How's this:

Right on the spot!!

 Thanks!

 Where can I learn how to write these formulas?

Hopefully someone else can recommend a book or something, but the best I can recommend is to tinker and experiment a lot, and lurk these forums.  As with anything else, there's no substitute for experience. :-)