language question

[kuroi]

just one more thing! I have to replace ONLY the define words thate are in english.

I'm not sure that I understand the question. So for clarity

define('BOX_HEADING_WHATS_NEW', 'New Products');
in english.php

becomes

define('BOX_HEADING_WHATS_NEW', 'Novi proizvodi');
in croatian.php

Good luck.