Link copied posts to the original

hi!

I was wondering wether there's a way for me to link the copied post to the original? Been looking in the files and found that there's a transient being set when copying which I can check in a save_post filter. But this only lets me know wether the post being created is a copy, not from where it's coming!

All I need is to set a meta value on the copies with the original post link or possibly the post id and blog id (even better). Any help here?

Thanks in advance!
/Jonathan