Write out your equations. Assuming that they are differential equations, look at any standard solver. If the equations are stiff, look at BDF methods. If non-stiff, Runge-Kutta is usually fine. If the equations are extensive then look at Adams-type codes.

If you have a stochastic element then good luck! I've never dealt with that.

It is not clear that what type of equation you used for modelling. If time variable is continuous, then used ODE45 solver in Matlab; if time variable is discrite, then used 4th order R-K- Method to get your desired results.