  The magnetic order-disorder layering transitions of a spin-1 Ising model are
investigated, under the effect of a variable surface crystal field
$\Delta_{s}$, using the mean field theory. Each layer $k$, of the film formed
with $N$ layers, disorders at a finite surface crystal field distributed
according to the law $\Delta_k=\Delta_s/k^\alpha$, $k=1,2,...,N$ and $\alpha$
being a positive constant. We have established the temperature-crystal field
phase diagrams and found a constant tricritical point and a reentrant
phenomenon for the first $k_0$ layers. This reentrant phenomenon is absent for
the remaining $N-k_0 $ layers, but the tricritical points subsist and depend
not only on the film thickness but also on the exponent $\alpha$. On the other
hand, the thermal behaviour of the surface magnetisation for a fixed value of
the surface crystal field $\Delta_{s}$ and selected values of the parameter
$\alpha$ are established.
