  We study the behavior of the critical Casimir force and its interplay with
the van der Waals force acting between two parallel slabs separated at a
distance $L$ from each other confining a non-polar simple fluid or a binary
liquid mixture. The surfaces of the slabs are coated by thin layers exerting
strong preference to the liquid phase of the fluid, or one of the components of
the mixture. The slabs influence the fluid by long-range competing dispersion
potentials. Under such conditions one usually expects {\it attractive} Casimir
force governed by universal scaling function to which the dispersion potentials
provide only corrections to scaling. We demonstrate, however, that below a
given $L<L_{\rm crit}$ the competition between the effects due to the coatings
and the slabs can result in {\it sign change} of the Casimir force when one
changes the temperature $T$, the chemical potential of the fluid $\mu$, or $L$.
The last implies that by choosing specific materials for the slabs, coatings
and the fluid for $L \lesssim L_{\rm crit}$ one can realize {\it repulsive}
Casimir force with {\it non-universal} behavior which, upon increasing $L$,
gradually turns into an {\it attractive} one described by an {\it universal}
scaling function for $L\gg L_{\rm crit}$. We presented arguments and relevant
data for specific substances in support of the experimental feasibility of the
predicted behavior of the force.
