Modified Euler's method expansion

suggest me to modify the following Euler's method expansion code so as to avoid the calculation of k2 two times

function []=EulerM(fn,a,b,y0,h)

x1=a;
y1=y0;

while(b>x1)
    k1=y1+h*feval(fn,x1,y1);
    k2=y1+h*(feval(fn,x1,y1)+feval(fn,x1+h,k1))/2;

      while(abs(k1-k2)>0.0001)
          k1=k2;
          k2=y1+h*(feval(fn,x1,y1)+feval(fn,x1+h,k1))/2;
      end

      x1=x1+h;
      y1=k2;
      fprintf('when x=%5.2f y=%5.4f\n',x1,y1)
  end