Install Files Conditionally

I'm a newbie so please bear with me.

How do I write a script to install certain files ONLY if they're NOT found at the destination directory?

TIA for your help.

MB

Please go to the manual, and search for 'file exist'. Having learned that, search for 'overwrite', because that's a better solution. http://nsis.sourceforge.net/Docs/Chapter4.html