at first, thank´s for your fast answer.
i don´t build with ANT the application, because the application is a RCP (=Rich Client Platform) application.
For this reason, i just use the export manager from the *.product-file which is provided from eclipse.
it´s important, that the path to the application dir is not hardcoded, because the application will lie at different working stations at different places.
therefore the path has to be set finally at startup time from the exported application.