Zoran,
Make your translations table based and display all strings by looking up the string in the table and selecting the user's chosen language. This will only require you to completely rewrite your entire application, unless of course you haven't written the app yet. Then it only requires that you plan and design the table based string management. This should only take a compatent programmer a few months of work to get right and thoroughly debugged. Of course for few hundred dollars you could buy it done already from Steven Black. But if you have the time and your hours are not worth the same money then you can certainly write it yourself. I doubt you will find anyone willing to write it for you without charge though.