Workplace Free Parking Spots

I need an iPhone app. I would like it designed and built. What is it about? At my workplace there are 100 employees and 40 of them have only a private parking which is numbered and no one else should park in this parking lot during the working day. During the holiday season or in case of illness of one of these 40 people, these parking lots are very often vacant simply because they will not be passed on. My idea is to develop an app where all 100 employees have access to it and these people who have a parking space can tick different dates on which their parking spaces are freely available. The remaining employees who are interested in those free parking spaces can register under the desired time periods. I need the flexibility in this app to be able to add people who want to participate in this app or later even remove people from it. A notification should appear when parking spaces are free so that the employees who are interested in those free parking spaces, can enter. If the entry is then filled for the desired period then this entry can not be taken by anyone else. However, if you change your mind anyway, you have to be able to unlock the parking lot.