One user at a time : In the instance where there are a number of people required to work on a spreadsheet, they can only access it when no-one else is working on it.
Spreadsheet: A table of rows and columns, free for the entry of data, or formulae for calculating actions on those data. Each row or column is said to contain many 'cells' and these cells serve as 'homes' for every shred of information.
Judging by this fact, the recommended course of action is to hire the services of a specialized company, a firm that will take care of all the details and subtleties of the spreadsheet programming in your place, and provide you with a ready-made or tailor-made spreadsheet solution that outperforms your expectations.
Rather than having to go through the pain and suffering of learning a new technology and having to experience trial and error development, the best route would be to acquire the services of a consultant, who can identify your needs and create a customised solution. Obviously, the cost of such a project would depend on the size and complexity of the spreadsheet and your requirements. However, you might be surprised at how cost-effective this project would be.