  We extended the Broad Histogram Method in order to obtain spectral
degeneracies for systems with multiparametric Hamiltonians. As examples we
obtained the critical lines for the square lattice Ising model with nearest and
next-nearest neighbor interactions and the antiferromagnetic Ising model in an
external field. For each system, the entire critical line is obtained using
data from a single computer run. We also discuss the accuracy and efficiency of
our method.
