  We present a concrete and consistent procedure to generate one kind of
non-perturbative superpotential, including the gaugino condensation corrections
and poly-instanton corrections, in type IIB orientifold compactification with
four Kahler Moduli. Then we use this kind of superpotential as well as the
alphaprime-corrections to Kahler potential to fix all of the four Kahler moduli
on a general Calabi-Yau manifold with typical K3-fibred volume form. In our
construction, the considered Calabi-Yau threefolds are K3-fibred and admit at
least one del Pezzo surface and one W-surface. Searching through all existing
four dimensional reflexive lattice polytopes, we find 23 of them fulfilling all
the requirements.
