Inside the same document? I assume you have Sharepoint multi-authoring enabled.

I would put the sections inside Rich Text Content Controls and apply tags to each of these CCs which enable you to assign approvers. Then you would need a series of macros to lock/unlock the CC according to the user's name. The ContentControl OnEntry macro for instance should look at the CC tag to work out if the CC should be unlocked for that user. You would also need to lock the CC on exit so others can't edit it.

The macros would probably need to be in a template saved locally and NOT on Sharepoint so you get a chance to have them running since your IT security settings might disable macros if they are in the Sharepoint doc.

__________________
Andrew Lockton
Chrysalis Design, Melbourne Australia