LaTex bibliography 'natbib' (Harvard) fix for URLs Lastchecked

I use BibDesk to manage my sources. For sources from the Internet, the date of access must also be listed in the bibliography according to Harvard citation. I combine the two types 'misc' and 'webpage': misc gives me - Title - Author webpage provides - URL - Lastchecked (yyyy-mm-dd) Natbib cannot display the field 'Lastchecked' so I use a regex in my .bib file: Lastchecked = {(\d{4})-(\d{2})-(\d{2})} Note = {[Online, Accessed on $3.$2.$1]} This will output sth like this: Author (YYYY), ‘Title’. [Online, Accessed on dd.mm.yyyy]. URL: https://example.com