Nuget Pack: exclude specification files!

Hi!

I'm using Nuget Pack as one of my steps of a Build.
I know I can set Specification Files using wildcards, for example: **/*.csproj

The question is, how can I exclude some of the matches?

This can be easily done, for example, in a nunit step, where I can set wildcards on "Run tests from" and "Don't run test from"

Thanks!