Lightroom :: How To Auto Set Keyword When Exporting Image

I like to keep track of what I've exported and uploaded to Flickr and other sites and what I've sent out to people. It seems tagging my images with some appropriate keyword is the best way to do this. Such keywords as "Flickr" or "Facebook", etc. But I the only way I can do this is to remember to manually apply each such keyword when I do the export. It would seem to me to be wonderfully simply if I could, in the export form, do something like "Add keywords:" and list keywords that would be added to each image exported through that form.
 
Is there another way to track such usage other than with keywords?