Customizable CSV downloads with additional information

[huzaifazoom]

Hi,
Can I customize my downloads, as in add descriptions and meta-data of my own?
The current downloads have a direct correspondence to the displayed data, but I have not been able to find a way to add supplementary information to the downloaded file.
If someone could point out how to patch into the existing download code, extend it perhaps, so that I may write my own handler to download the csv file, that would be great.
Huzaifa.