Natbib sort option

[Guillaume Larocque]

Hi, I would like to use the natbib package for my citations in Lyx
with the [sort] option so that multiple citations are ordered into the
sequence in which they appear in the list of references. However,
specifying

\usepackage[numbers,sort&compress]{natbib}

in the preamble of my document produces an error when compiling to
pdf. It says the package has already been called. Is there any other
way of doing this in Lyx?

Thanks,