I'm trying to find a way that a certain user could only have access to certain accounts.  So for example we have 100 different parent accounts (and 1000 plus child accounts associated with them) and we would only want the new user to be able to see child accounts associated with 1 particular parent account. 

I can see how to set permissions on the 'field' level, but this assumes that you want every user to be able to see every single account on the account level.

Any help is appreciate, thanks!

Aaron