  Q-LET is a FORTRAN 77 code that enables a quick estimate of the gravitational
lensing effects on a point- or an extended source. The user provided input
consists of the redshifts, angular positions relative to the source, mass or
velocity dispersion estimate and halo type for the lens galaxies. The
considered halo types are the Navarro-Frenk-White and the Singular Isothermal
Sphere. The code uses the so-called multiple lens-plane method to find the
magnification and intrinsic shape of the source. This method takes into account
the multiple deflections that may arise when several mass accumulations are
situated at different redshifts close to the line-of-sight.
  The Q-LET code is applied to the recently discovered supernova, SN2003es,
which is likely to be of Type Ia as its host galaxy is classified as an
elliptical. We find that SN2003es is likely to have been significantly
magnified by gravitational lensing and that this should be considered in high-z
studies if this SN is to be used to determine the cosmological parameters.
  Q-LET was motivated by the supernova searches, where lensing can be a
problem, but it can also be applied to any simple lens system where a quick
estimate is wanted, e.g. the single lens case.
