Eclipse + Ant

So I'm working on a project where I want to  be able to generate a number of jar files from a common codebase that will each contain different subsets of the classfiles in the codebase.  Right now I have a number of batch files doing this, but it's a clunky solution, and things are just going to get uglier with time.  I was thinking of redoing the scripts with Ant, from what I understand you can automate jar builds from an Ant build script.  I was wondering if anyone has any advice on setting up and working with ant scripts within eclipse.  Is it possible to use Ant to generate a jar file that will only contain a few class files from a larger set of class files?

Cheers guys and gals,
Rob