Using External Jar Files In Your Custom Ant Task Classpath.
It took me a while to figure out that I could specify several items in the classpath attribute of the
taskdef tag in my build.xml file.
Here is one example:
<taskdef name="CreatePartition"
classname="org.wwre.ant.tasks.xis.CreatePartition"
classpath="build/classes;${xis.client.jar};${log4j.jar}"
/>