Event subscribers are a possibility for standard insert, modify, delete and validation occurrences. For something like address formatting you can add the format address codeunit as a variable in your custom procedure and then call a global function from that codeunit. The global part means that the function in the standard codeunit cannot say “local procedure” as it is just local to an instance of that codeunit.
This type of codeunit usage is used across the application as standard.
