Hi Tintin,
In the Functions>>Programming>>File>>Advanced palette (or the express VI palette), there's a File Dialog express VI that sounds like it'll do what you want, or could be a good starting point once converted into a normal VI - you can configure it to allow the user to select a file, folder, or either file or folder, limit to new or existing files, and pass in a dynamic "start path" for where to open the file browser. It also allows you to set only certain file types to appear in the browser (.csv, for example).
The core VI for this express VI is just the File Dialog primitive, also found in the Advanced File palette, but I'd recommend using the express VI to get a better idea of how it's configured.
Regards,
Tom L.