Using Symbolic to derive equations

I have asked a similar question before "http://communities.ptc.com/thread/34460" however as I find out the answer did not fully cover my question. The missing point is in the argument

Here is what I am looking for since I already have a subroutine that calculates the derivative of

I did that and few other derivations by hand. I wish there is a way I could do that by Mathcad