Radon-222 Gas 2-Dimensional Transient Diffusion Simulation in Soil Using Octave/Matlab

I've already make a few code to simulate or make a model of radon gas diffusion trough soil for my essay to complete bachelor degree. And the program worked and obtained the estimated result (graphic/surface/curve) as it should be based on the algorithm. But there's a problem I can't solve, the result in form of graphic or surface won't work following the specified time, in example: if I specify the time (Nt) for 100 hours, the curve will moving and reshaping to the form based on the diffusion equation from the initial condition (IC), however the graph would stop at 6 hours, so the result would be the same for 6 hours, 100 hours, 500 hours, and so on. I new to this kind of programming, so I need your skill so the program would running (the result graph that contains concentration value) or would changing until the specified time that we've already specified. Here I attached my algorithm (you only need to see the table section) some of the same program and output in format ".m" so you can run it and open it using Octave or Matlab