Using your posted workbook

This formula sums 2013 cells where the corresponding 2014 cell is greater than 0
N2: =SUMIF(B3:M3,">0",B2:M2)
And this formula, copied across, calculates the percent difference
B4: =IF(COUNTIF(B2:B3,">0")=2,(B3-B2)/B2,"")
Is that something you can work with?