Visit your package in the package manager at /acs-admin/apm and click on the Internationalization link (I18N). From there you can choose to transform your adp pages to using a message catalog instead of hard coded strings. That process is semi-automatic.
Let me know about your questions after you have carefully read the instructions there.
The use-case you are describing is fully supported by OpenACS on cvs head and in the upcoming 5.0 release.
I visited the site /acs-admin/apm but i could not able to find out Internationalization link at all. plz help as this is an important thing to our website.