How to use a Loop in an optimization problem?

Hi everyone, I'm trying to find out an optimal capital structure, which means to find out the optimal variable c that maximizes -g(c). In order to do that I need first to solve a nonlinear system, which is my function Fun(x), for a given initial c0 and x0. Then using the optimal value x, I can find the value c that maximizes the -g(c). My problem is that I want to make a loop that stops when the value of c using in the nonlinear system is the same that the obtained value from the maximization problem, but everything I try it's not working.

My main code is:

    function [x,c,err]=newdim3(Fun,x0,c0,~)

    global xi tau_e tau_i r mu k epsilon; 

    tol=10^(-3);

    c=c0;
    x=x0;

        for j=1

           options=optimset('MaxFunEvals',1E5,'MaxIter',1E5,...
          'TolFun',1E-32,'TolX',1E-32,'TolCon',1E-32);

           [y,fval]=fmincon(@(y) Fun(y),x,[],[],[],[],...
    [0 1 -Inf -Inf -Inf -Inf],[1 Inf Inf Inf Inf Inf],[],options);

           a1=y(3);a2=y(4);b1=y(5);b2=y(6);

           if (c>1)

                tau_e3=tau_e*epsilon;

           else

                tau_e3=tau_e;

           end  

           options=optimset('Display','iter','TolFun',1e-8);

           g = @(C,y) -xi*((1-tau_e3)*((1/(r-mu))-(C/r))+...
         a1+a2+(1-k)*(((1-tau_i)*C/r)+b1+b2));  

           C = fminbnd(@(C) g(C,x),0,y(2),options);

           err=abs(C-c);

           relerr=err/(abs(C)+tol);

           if (err<tol|relerr<tol)

               c=C;

               break;

           end 

           c=C;

           x=y;

           iter=j;

        end

    return