modify attachment on download

[Hornstar]

I am not sure if this is possible, or if it is available, but I am requesting some information about this, and what I should be asking a coder, if I was to pay for it, or if they were to make it.

Kind of like what vbulletin.com does in their downloads, when you download it, it modifies the file, so it includes customer info in to the actual file.

I would like to do this as well, but not sure what type of files it could be done with, if it can be done forum wide, or if it would need to be done in a members section (all of that information I am interested in).

But any info on this would be great, and if you feel like coding it, that would be even better!

Thanks.