how to make the contents of a file disappear after x numbers of days or at date

[user1]

Anybody know of a way to make the contents of a file (txt, html, jpeg, 
png, mp3, ogg etc.) disappear after a certain number of days.

To make the whole content or a selected part of a file to disappear.

The charateristic must be hidden in the file and not to be removed by a 
copy.

I should be a kind of wipe operation :-)