How to write IPTC metadata to files without opening the file?

HI,

I'm trying to run a script (preferably in JS) that allows me to write metadata to a file. I can acheive this very easily by opening the file, but I'd need to batch process many large images, so opening them would cause severe slowness. The purpose of adding the metadata to the files is to search upon them in Bridge.

We're using CS5, but have CS6 if it's better to use.

My Script

// set current doc ref

var docRef = app.activeDocument;

// Set caption in active document

docRef.info.caption = "Some Meta-Data";

Do I need to use bridge to write the metadata without opening the file? Or can running the script in PS allow me to do so?

Thanks,

Tom