Is it possible to numerically solve a differential equation (in Mathematica) that is composed of the solutions to another numerical differential equation such as Sol1=NDSolve[f'[x]= f[x].....] Sol2=NDSolve[g'[x]= G( g[x], f[x] ).....] where G(x) is the a function of the interpolating function produced from the previous ODE? I have tried writing the G(x) as by replacing all the f[x]'s with Evaluate[f[x] /. Sol1] but I get the error "NDSolve::ndfdmc: Computed derivatives do not have dimensionality \consistent with the initial conditions." Any suggestions? Thanks!