pass an file into antfile when using ANT task

For example, I have two build.xml: build.xml and subbuild.xml. In the build.xml, it will use an ant task to call and run the subbuild.xml like this:

<target name="antCall1" >
    <ant antfile="${basedir}/cache/subBuildTarget/subbuild.xml" />
</target>

My question is like this: I have an "test.xml" next to the build.xml. How can I modified the codes above so that I can pass the "test.xml" into the subbuild.xml and do some operations in the subbuild.xml?

Actually, I want to pass the "test.xml" as a of a task in subbuild.xml. I am just confused about how to let the subbuild.xml get accessed to the "test.xml" in the build.xml. Thanks!