The formula

INDIRECT(SUBSTITUTE(TEXT(A2,"mmm yy")," ","_"))

turns the Cell value in A2 into the name of the named range, A2 is 1/1/2014, TEXT makes it a string in this format "Jan 14" then SUBSTITUTE takes the space out and replaces it with an underscore (= Jan_12) since named ranges cannot have spaces in them. INDIRECT makes XL look at the referenced 'indirectly' within the formula brackets, rather than the text as a 'text string'. In other words the formula will SUM "The range that is referred to as 'Jan_14' ".

The new attached one does away with the column you say you can't have, does this help?

Sum Values Using Row and Column Data... named ranges.xlsx

If so, please give me a 'rep'. Thanks