adding manifest entries

[G.L. Grobe]

 I've got an EJB app that creates jar files, and the classes in these
jarfiles depend upon a third party jar. Yet my app can't find the classes in
this jar. I have nothing in my MANIFEST.mf files (the ones created by Ant).
So how do I tell Ant to add the classpath for 3rd party jarfiles I'm adding?
If I create a MANIFEST.mf, it just get's ignored by Ant.

Any help much appreciated.