  Recently, Chartas et al. (2001) detected a rapid X-ray flare in the
gravitationally lensed, multiple image quasar RX J0911.4+0551. Dramatic events,
such as rapid X-ray flares, are useful in providing high precision measurements
of the time delays between multiple images.
  In this paper, we argue that there is a new possibility in measurements of
time delays between multiple images of gravitationally lensed quasars;
constrain the locations of putative flares that give rise to the intrinsic
rapid variabilities of quasars. The realization, however, of these goals cannot
be presently achieved due to the limited accuracy of the current measurements.
We predict that timing flares with accuracies of the order of a few seconds
will be needed to probe the location of the flares. Our proposing method will
work with better instruments in near future, such as XEUS.
