Sum multiple Index Match Lookups!

This one should be an easy one!
I have a file that gives me a cross match based on style and month.
However, if the user chooses say, March for example, I want the formula to add January and February as well.
I know there is a along complicated way to do this where I add Index and Matches and maybe several nested if-thens but if I could get one formula, that would be great!

So Basically instead of =index(a1:z1000,match(Style,a1:a1000,0),match("Jan",a1:z1,0) + index(a1:z1000,match(Style,a1:a1000,0),match("Feb",a1:z1,0)
have it say something like
=index(a1:z1000,match(Style,a1:a1000,0),match({"Jan","Feb"},a1:z1,0).
Thanks

Book1.xlsx
sorry here you are

in theory, but actually the equation is more than just months taht it looksup, it is actually a month and another value that it looks up, for example, it is actually not just january but "januaryunit", "Januarycost", so the lookup value horizontily is not just a month.

Book1-3.xlsx
Sorry
try this

Originally Posted by mcmahobt

Assuming the values in row 2 are only there for the INDEX/MATCH, and assuming you won't be using that approach anymore, can I alter that data?

Yes you can my friend

I will try that, in the meantime, I have found a way I like but the sumproduct formula keeps giving me errors cause the sheet has alot of errors and blanks and texts
how can I make this formula to ignore all those errors and blanks in the data array without having to manually change data to suit the formula.
=SUMPRODUCT(('2015OTB'!K16:N23)*('2015OTB'!A16:A23=A16)*(ISNUMBER(MATCH(K2:N2,A1:A2,0)))*(ISNUMBER(MATCH(K14:N14,A3:A4,0))))

thanks