defining a constraint in fmincon

Hi guys, I want to define linear constraints of the form: A*x <= b of my S to be like: minS <= S(t) <= maxS

% My storage function is this one:
function S=storage(init_s,inFlow,x,N)
      T=totalflow(x,N);
      S(1) = init_s(1) + inFlow(1)-T(1);  
      for ii = 2:N  
              S(ii) = S(ii-1) + inFlow(ii)-T(ii);   
end

Tried solution see below pls, but I get S after some time steps higher than my maxS. Any clue why?

%I have tried this one but Smax is exceeded almost all the time. 
c1(:,i) = init_s(:,i) + cumsum(inFlow(:,i)); 
b2(1:N,i) = maxS(i)-c1(1:N,i);  %upper storage limit
b3(1:N,i) = -minS(i)+c1(1:N,i); %lower storage limit
b = [b;b2;b3]; %addition to previous constraint
s = -1*sparse(tril(ones(N)));
s = [s s];
A = [A;s; -s];

Any idea or tip? Thanks a lot!