Thank you for your help. I have received a response from booking.com which resolves the problem.
'Please be informed that we have updated it and from now on you are able to set up these particular restrictions (arrivals/departures on a certain days). You can easily do it via Extranet - Rates & Availability - Calendar - Press on Standard Rate - No Departures/No Arrivals (Edit).'
Thank you for your help. I have received a response from booking.com which resolves the problem.
'Please be informed that we have updated it and from now on you are able to set up these particular restrictions (arrivals/departures on a certain days). You can easily do it via Extranet - Rates & Availability - Calendar - Press on Standard Rate - No Departures/No Arrivals (Edit).'
If this applies to you I hope it can be helpful
Thank you for your response but Booking.com claims to offer these features. Can anyone else help?