How can I stop matlab pde solver in pde tool box when solution is unstable?

I am solving two coupled time dependent PDE eqations using pde tool box.The simulation box size is x=6 and y=10.Currently I solve it properly and acces the solution data using results = solvepde(model,tlist); u = results.NodalSolution(:,1,:);

What I need to do is now to stop the code when the solution u is unstable along the y axis.That means I want to monitor solution of u along y axis while running the code and stop it when it meets a criteria that I want.(For example I want to stop the code when solution of u along y equals to 0)..How can I do it using pde tool box?

Here is what I tried so far.Is there easy way to access the results while code is running?.That is I want to access the solution for each time step.

%calculate solutions
n=4000;
tlist = linspace(0,200,n);
partial=zeros(49,1);

for i=1:n
     results = solvepde(model,tlist(i:i+1));
     u = results.NodalSolution(:,1,1);
     v=results.NodalSolution(:,2,1);
     u1=results.NodalSolution(113:161,1,1);
     u2=results.NodalSolution(1,1,1);
      u3=results.NodalSolution(4,1,1);
for j=1:49
    partial(j)=u1(j)-0.5*u2-0.5*u3;
end
sigma=sum(partial);
if sigma>1e-4
    disp('verified')
    return
end
end