  Numerical studies in random systems are plagued with strong finite-size
effects and boundary effects. We introduce a window-measurement method as a
practical solution to these difficulties. We observe physical quantities only
within a subsystem located in the midst of a whole system and scale them with
the correlation length estimated in the subsystem. Both equilibrium data and
nonequilibrium data with different system sizes and different window sizes fall
onto a single scaling function. It suggests that the correction-to-scaling
terms become very small. We confirm the validity in the $\pm J$ Heisenberg spin
glass model in three dimensions. The spin-glass and chiral-glass transition
temperatures are estimated to be very close to each other.
