VB code for runge kutta second order numerical integration

hi all,
I am working on RK numerical integration to solve second order differential equaion. I have the code from "engineering with excel". But it is not complete general form of second order eqn.

This code is in the attachment named "rk-vbcode.txt". this works well when there is only one term on the right hand side of the equation. like a constant term. But showing wrong results when the first deivative and other terms are added. I have compared them with the results from maple & mathcad.

can any one has the code please post it here or mail to [email protected].

Thanks