Editing the node structure in NS2

Hi,
I am working on creating a strategy for implementing Self Organisation in
MANETs. For the same, I also need to edit the structure of the node so as
to include a credit value and then need to put my controller function in
the DSR protocol implementation of NS2. I want to edit the credit value of
the node when a node successfully forwards a packet. How can I model this
kind of a behaviour? Thanks in advance