Finding the time duration of an oscillation on a graph

% Dear Users,
% I have an oscillating voltage curve depending on time (please see the document on the attachments)
% t_clear= Clerance Time
% t_e=Execution Time
% u_ref=Reference Voltage
% After the t_clear=0.2 s, I want to calculate how long the oscillation stays until t_e
%                       1.) out of +10% and -10% of u_ref (depends on u_ref value)
%                       2.) out of +10% and -10% of u_ref=1 per unit (that makes u_min=0.9 and u_max=1.10 per unit)
% Thanks in advance!

%The related part of the code as below:
files = {'Test1','Test2','Test3','Test4'};

C = linspecer(4,'qualitative');

path ='...';

xlimup =  1;
xlimlow = 0;

n=2;
windowSize = 100;
b2 = (1/windowSize)*ones(1,windowSize);
windowSize = 10;
b1 = (1/windowSize)*ones(1,windowSize);

dispU = [2 2 2 2];
dval = zeros(101011,4);
i_pos = zeros (1, length(files));
i_neg= zeros (1, length(files));
refval = zeros (1, length(files));
lastval = zeros (1, length(files));
minU = zeros (1, length(files));
ideal = zeros (1, length(files));
t5 = zeros (1, length(files));
t10 = zeros (1, length(files));

for ff = 1:length(files)   
    val = dlmread(strcat(path,'\',files{ff},'.csv'),'\t',2,0);
    
    % Ideal conditions
    refval(ff) = mean(val(1:100,dispU(ff)));
    
    % Time difference, te-tmin
    deltaT = te - tc;
    
    % Ideal area
    ideal(ff) = refval(ff) * deltaT; 
    
    % Deviation
    idx = find(val(:,1) > 0.2);
    dval = val(idx,dispU(ff))-refval(ff);

    i_pos(ff) = trapz(val(idx,1),dval.*(dval>=0)); 
    i_neg(ff) = trapz(val(idx,1),dval.*(dval<0));
    
    % I want to change this part!
    [~, idxt10] = min(abs(dval +  0.1)); 
    
    % I want to change this part!!!!!!!!
    t10(ff) = val(idx(1)+idxt10,1);
    
    lastval(ff) = val(end,dispU(ff));
    
    val(:,dispU(ff)) = filter(b2,1,val(:,dispU(ff)));
    minU(ff) = min(val(100:end,dispU(ff)));
    
    % Plot the figure
    figure(1)
    grid on
    hold on

    busU = plot(val(:,1),val(:,dispU(ff)),'LineWidth',lw,'Color',C(ff,:),'LineStyle','-');  
end