Booking system / calendar

We are 4 brothers and sisters who share a summer cottage. We want to make a booking system for this house. We have the priority of the house alternately one week at a time. Before you are using the house you have to make a final reservation in the system. If you want to make a reservation going into a new week, the system sends a mail to the brother or sister who has the priority of that week. The mail should content a request for this reservation. We have added a picture of what we want it to look like. The idea is that each of us has a color (yellow, red, blue and green). Example (look at the picture): My color is yellow and my "priority week" is the first week in May and it is therefore colored light yellow. If I want to make a reservation from the 3rd of May until Sunday, these days turn into a darker yellow. If I make a reservation going from the 3rd of May until the 10th of May, the system sends a mail to the sister or brother (who has the priority of the next week) with a request of these days. The mail should content a simpel question "accept or deny". If he or she chooses accept, the days turn dark yellow and if he or she denys the system sends a mail back to me telling that it is not ok and doesn't make any reservation at all... Our names and colors: Klaus - Green Astrid - Red Finn - Blue Sven - Yellow If you have questions please feel free to contact me...