Writing a loop that goes 12 months at a time for 62 years

I need help on how to write a loop that would go 12 months at a time for 62 years and sum the difference between the max and min of a function.

[dpb]

Not enough info but

for m=1:12:62*12+1
  ...
end

would cover the span in months.

But, look into rowfun and grouping variables and you may well do without explicit looping entirely...