  Selectrons may be produced in pairs at LEPII if their mass is less than about
100 GeV. Preferably, they decay into the lightest neutralino plus an electron.
In a scenario where selectrons are observed at LEPII, we show that: (i) in a
first stage where experimental errors are large, the measurement of the total
cross section of selectron pair production, the selectron mass, and the
lightest neutralino mass, allow us to validate or rule out the Minimal
Supergravity Model in its simplest form, and that (ii) in a second stage where
precision measurements are available, the value of $\tan\beta$ can be
determined together with the rest of the parameters that specify the Minimal
Supergravity Model and, with them, the entire supersymmetric spectrum can be
calculated. We include experimental constraints from sparticle searches,
$Z$--pole physics, stability of the lightest supersymmetric particle (LSP) and
the decay $b\rightarrow s\gamma$. In these scenarios, small values of
$\tan\beta$ and negative values of $\mu$ are preferred, and the lightest Higgs
mass satisfies $m_h<110$ GeV, which makes it likely to be detected at LEPII.
