The ANT_HOME variable has to be a reference to the directory where the bin folder is found such as C:\Apps\apache-ant-1.8.4-bin\apache-ant-1.8.4\
The PATH reference can than be a reference to the ANT_HOME variable and the bin folder such as %ANT_HOME%\bin
example:
SET ANT_HOME=C:\Apps\apache-ant-1.8.4-bin\apache-ant-1.8.4\
SET PATH=%ANT_HOME%\bin