Operations on cell arrays over lagged rows

If I have a cell arrays of different dimension, say for i=1 to 10, a cell P{i} of (1:n-1,3) and another Y{i}(1:n,3). I want to make a computation within loop over all element of P and Y for each i like sum (P{i}(j,:).*Y{i}(j-1,:)) such that for each i a row of P is multiplied by the previous row of Y what is the code??

[Niveen El Zayat]

I tried this code

indx=2:n; P{i}.*Y{i}(ind,:);

Is that right??