Changing lens and aperture Exif data with script possible?

I'm photographing with manual lenses that do not transmit exif data about lens type, focal length and aperture. I was looking for a Bridge addon that allows me to add this information, but found nothing. Is it possible to change this field with a Bridge script? I've read the documentation and found no evidence that it isn't allowed, but I've read on another site that it's impossible to change this kind of fields.

Can anybody shed some light on this? If it's generally possible I would write such a script.