I would like to pick out specific christoffel symbols once maple calculates them. Right now I am using CoefficientList, but I would like a more direct way, as I am working with someone using Maple 17, and they are put in a different order in the CoefficientList. Here is the bit of my code I would like help with.

So I am trying to solve a given ODE using calculated christoffel symbols found by maple, and in order to get the correct christoffel symbols, I need my function to be r=x-x_s, where x is not a function of t. However, I then have to solve the ODE where x is a function of t. Maple used the r value to find the christoffel symbols which has x in it, and now I want to find the origonal function of x(t), but I can't have x and x(t) in the same ODE. If I change r=x-x_s to r=x(t)-x_s, I get the wrong christoffel symbols. How can I solve my ODE?