I have made a POS System for a client of mine using MS Access Server-Client approach.

He asked me to brand his software to allow only a certain "number" of users (cashiers) to access the POS System, and must be determined to the license his client will buy.

EX: 10 User License = 10 Cashiers ( not necessarily 10 users, it can be 30 users, shifting) = it means 10 PCs will be installed with the client software I made.

How and where do I put the logic that will determine if it is licensed or not.

What I have done:

I have created a serial key generator using Name. Problem is it can be duplicated once you give than name+serial combination, it would still work.

I am counting the number of users logged at a time. This could be problematic as I am using MSAccess and not MSSQL. I have scrapped this idea,

He also asked me if I could just put serial+mac address combination. That I could do but he will have a hard time implementing it and selling it if he needs the mac address of every computers to be installed with my POS.

I am at lost on what can I do. Would like to ask for tips and suggestions.

Thank you.