@Steven65 There is a difference between a booking request and an inquiry.
If it is an inquiry all you have to do is send the guest a message letting them know that those dates are not available. The message counts as your response and you do not need to "pre-approve" or "decline."
If it is a booking request the guests has given their credit card info and once you click accept their card will be charged. Why people give up their CC info for a purchase (the selected incorrect dates) they do not want is beyond me. If I were you, I would say: "Unfortunately, the dates indicated in your message are not available but the dates that you selected as part of your booking request are. I would be happy to approve your selected dates and reservation will be confirmed and your credit card charged. If you do not wish to reserve these dates please withdraw your request by X time today."
The guest will likely withdraw their request pretty fast and you will not need or approve or decline.