Best way for deploy excel with .net dll reference

Hi my customer has an excel files with macros with call a vb6 dll functions for CRUD operations in Access db. The first phase of my project concern to migrating the vb6 dll to .net 4.5 (c#) and the Access db to SQL SERVER. Obviously the migration cause excel macros modifications to allow existent macros make calls to .net methods instead of vb6 function calls. After I'll complete this migration I must put the modified excel file and .net dll in a intranet web page under authorization control because only some people can use it. So I don't know what is the best way to do this, because the excel for work correctly need a reference to dll. I would like avoid that the customers manually add reference to dll in their pc. I wondered among other things if it would be correct to assume to put the dll .net in a shared folder of a server, make this shared folder accessible from all the PCs of customers, make sure that the excel put on the web page has reference to the dll on the shared folder and make sure that the db server is reached from the server where the shared folder is created. In this way from any pc where the excel is downloaded it should be possible to do CRUD operations on the db through the dll .net, right? Maybe is better transform the .net dll into a web service? Can you think of any other idea? Thanks in advance