Marching algorytm in Matlab

During work on on WiFi propagation project, I´m try to solve a problem with marching algorythm based on Huygens principe and physical optics.

This is defined by integral:

E(x2,z2)=sqrt(k*x1/2*pi*i*(x2-x1))*integral (from h1 to inf) E(x1,z1)e^(i*k*r) dz1

This integral is solved for vertical parts over real terrain example and for every point E(x2,z2) sums all additions from previous vertical slice (E(x1,z1) in distance r. I prepared this code:

for k=2:lengdel
for l=height(k):maxf
for m=height(k-1):max
len=sqrt(1+(l-m)^2);
shine1(l,k)=shine1(l,k)+(sqrt(k1./(2*3.14*1i)))*((shine1(m,k-1))^2)/2*(exp(1i*k1*len));
end;
end;
end;

But there is any problem with function that results go to infinity. Can anyone help me?