Please explain what you mean by this as its quite confusing. Your viewing an ad which has all the information etc etc and you place a bid so you already know what your bidding on hense you see my confusion in your remark.
If you bidding on multiple items, it would be good to have each bid item added to the Watch List automatically. To save book marking or remembering the direct link of each of the items you are bidding on. Just incase the bidder forgets.
Okay that makes more sense now. Quite easy actually if you want when someone bids successfully on an item for it to be added to there watch list then simply add this query in bold where noted to bids.php