Hey Raikar,
The concept you're trying to implement is called 6-wire resistance measuring. Here's an article that discusses the concept:
http://zone.ni.com/devzone/cda/tut/p/id/3486
In short, you use an opamp to null out any elements in a particular node that you do not want current flowing across. Let us know if you have any questions.
-John Sullivan
Problem Solver