Find array elements in another vector

Hi, everyone

I am stuck by MATLAB right now. I really appreciate if I could have your suggestion on this.

I have a vector "delta" where I would like to retract its value for further calculation.

This would be based on another vector showing a stage of "delta vector" as "NR" or others and if the continued epoch number of NR is bigger than 30 (if there are more than 30 epoch in NR present continually).

Then I want to find values of first three epochs and last three epochs in this continued NR in order to calculate the changes in the values.

So far my script looks like this, which I can know the sequence number of first epoch in each continued NR (2,j) and numbers of each continued NR (1,j).

i = 1;
j = 1;
delta = VarName5+VarName6+VarName7+VarName8;
continued_epoch_number = zeros(2,1);
for i=1:4320
        switch Stage{i}
        case 'NR'
            if Stage{i}==Stage{i+1}                 
                difference(i) = 1; 
                continued_epoch_number(1,j) = continued_epoch_number(1,j) + 1;
                if continued_epoch_number(1,j) == 1
                   continued_epoch_number(2,j) = i;
                end
            else
                difference(i) = 0; % if the next stage is other else
                               j = j + 1; % jump to next element
                continued_epoch_number(1,j) = 0;
                continued_epoch_number(2,j) = 0;
            end
        end
end

But I do not know how to move on to find those epoch and their values in "delta"

Perhaps, my description is not clear enough. I will do my best to explain my situation so please feel free to ask me about this code.

Best Regards