Delay differential equation,how to solve WITHOUT using any solver(dde23)????

I have to write a matlab code for a delay equation.I have already the main body but i can't make it work.Maybe there is someone who can find what i am doing wrong?Or maybe have another example?

h=.25;
r=5;
T=15;
D=0:h:r;
N1=length(D);
t=0:h:T;
N=lenght(t);
y(1:N1)=t(1:N1)*(t(1:N1)-r);
for i=N1:N
  y(i+1)=y(i)+h*y(i-N1);
end
figure(12)
plot(t,y)
figure(2)
plot(t(N1:N),y(N1,N))