  Future Sunyaev-Zel'dovich effect (SZE) surveys will detect thousands of
clusters, many of them at high redshift. We show how the SZE number counts as a
function of flux can be used as a useful way of constraining the cosmological
model. The constraints can be dramatically improved if redshift information is
provided for a small subsample of the observed clusters. In this work we
present the constraints in Omega_m and Sigma_8 expected for a combined
mm-optical survey. The mm survey (Planck) providing the cluster number counts
as a function of flux and the optical survey (GTC) the redshift estimation of a
small subsample of the cluster catalogue. We also show how it is possible to
get an accurate estimate of the cluster flux using a non-parametric component
separation algorithm and how using morphological redshifts it is possible to
make a high-z preselection of the small subsample to be observed in the
optical.
