There are many numeric approaches to solving sets of differential equations. As long as the numerical equations can be represented as a set of functions of the form: dy(x)/dx = f(x) you should find an appropriate solver. One family of numerical solvers is the Runge-Kutta family, and there are many others. Any numerical analysis book should have details. If you have an important point to make, don't try to be subtle or clever. Use a pile driver. Hit the point once. Then come back and hit it again. Then hit it a third time - a tremendous whack. --Winston Churchill