Hi,
Sure. Create a custom field of the type radio, and under the "data" area, select "MySQL query", and enter the MySQL query:
SELECT CURRENT_DATE() AS value UNION SELECT CURRENT_DATE() + INTERVAL 1 DAY UNION SELECT CURRENT_DATE() + INTERVAL 2 DAY UNION SELECT CURRENT_DATE() + INTERVAL 3 DAY UNION SELECT CURRENT_DATE() + INTERVAL 4 DAY UNION SELECT CURRENT_DATE() + INTERVAL 5 DAY UNION SELECT CURRENT_DATE() + INTERVAL 6 DAY
That will dynamically load the date of the current day plus the next 6 days in the custom field. That will be easier than creating a custom type of custom fields with the development of a plugin.