how to get current xy co-ordinates

[Rudhra <venkatru@ece.orst.edu>]

hello,
       I am developing a new protocol in ns for adhoc networks. As part of
the simulation I need to get the current x and y positions in a simulation
area of l * b.
(a) how do you define a area of simulation in ns according to user given
parameters
(b) how will you get the current x and y positions relative to that area of
simulation

your earliest help will be kindly appreciated
regards
Rudhra