CHARACTER SET Problem

Hi friends,
I have to read a file (coming in ISOLATIN format - .txt form) which contains czech characters & some of its content I have to upload it to our system's Database (8i)
Tables containing VARCHAR attribute. It shows me the correct characters when I ftp it from Windows to Solaris then from there I run the scripts to Upload that file to the system , but I find it is not showing me the correct Czech characters in the database,it shows some junk values instead. What can be the problem? Same System we use for uploading files in English version. So do I need to change NLS_LANG for ISOLATIN while uploading this file or any other parameter in the database?. We r getting UTF8 format files for other version i.e English. Any idea friends?????......