Divide by every N rows

I am trying to perform the following calculation, but every 52 rows the denominator needs to change from (1,1) to (52,1) then (104,1) etc.

Can someone please assist?

 rAPf(i,:) = ((tickPf(i,1) / tickPf(1,1))-1)*100;

Answer 1

[KSSV]

t = 1 ; 
for i = 1:n  % n should be your last index 
    if mod(i,52) == 0 
        t = i ; 
    end
    rAPf(i,:) = ((tickPf(i,1) / tickPf(t,1))-1)*100;
end