As other answers have mentioned providing the name of needed jar in the MANIFEST.MF file of the jar that you invoke is one way to resolve your problem.
During jar file (the one you invoke first) creation you can specify the manifest file which contains this detail so that it gets bundled with your jar.
The Java tutorial has a section on how to specify the Manifest file during the jar creation.
If you are using Ant as your build tool you can use the Ant task Manifest to create a manifest file. You can use the Manifest file thus created in the Ant task that builds your jar.
Also check this link which provides more details about the Manifest file.