looking down a column of cells until it reaches a tolerance

hi I want my code to read down a column and find the point where the person starts to jump i.e. the data deviates from bw (body weight) by +/- 10%. How do I do this? so far I have:

    if (I<=bw*0.05) && (I>=bw*0.05);
            peak_pwr(i,1) = nanmin (data1(1:to(i,1),5)); 
%peak power in coloumn E1 in all data with reference to cell found
            av_pwr(i,1)=nanmean(data1(1:to(i,1),5));
%average power in coloumn E1 in all data with reference to cell found
        end

Answer 1

[Image Analyst]

I think you mean 0.9 and 1.1 instead of 0.05 to get the +/- 10%:

if (I>=bw*0.9) && (I<=bw*1.1)