I think you're architecturally confused.

SQL Server is a server. Your application will submit an insert or update to the server, and any result from that gets sent to your application, not the user on the screen. SQL Server has no interaction here.

What you can do is return a message to the application, but it would need to handle that message and then display something. Alternatively, the way most people handle it and GSquared suggested, is that you use the front end to catch this before you submit it to SQL Server and pop a note to the client.

what is your front end, out of curiosity.