Om call list

I want an excel file which can generate algorithms to make an on call list for doctors. We have 3 types of shifts and we make on call lists every 3 months. The excel file should be able to allow certain doctors to choose how many on calls of shifts then want per month and according to that randomly attributed on the calendar. In addition to the other remaining doctors should be able be randomized in the on call lost. Of possible this calendar list should be able to available on cloud so that if some doctors want to change shifts so they can do that real time. Additional information about the project and shifts will be mentioned further on.