See the comment from Sinisa Hajnal.
They have provided a few reasons why a database is better than excel. There are several more, not least the fact that you would have to have Excel drivers installed on your
server in order to access the data. That can be an expensive overhead that is just not required.
Secondly, any functions and operations should not be in your "database" in this way - you should be putting these in the code behind, or as Stored Procedures / User Defined Functions on your actual Database.
Using Access would be a step forward from using Excel, but even that will come with it's own issues.
Consider using one of the many free database systems that are available e.g.
Free Database | Free SQL Server Database | Database Management Solution[
^]