Bulk editing accounts/leads

Hi, I'm in the Professional edition of SF. I would like to bulk edit a group of accounts and/or leads. I am transferring them from one owner to another, and I would like to add a note (in the Description field would be fine) to the effect that Rep X used to own this account/lead. It is a large group of accounts (600+) so doing this manually is not an option. Is there a way to bulk edit a field, either as part of the Transfer Accounts process, or before/afterwards using some sort of filter?

Thanks.