Chat customizing HELP

Hi, I’ve been looking for a script for a long time so that after entering a certain symbol, for example @, the message after this symbol will be marked in the box as in the screenshot.

Please help me find!

I know that this is easy to do, but I don’t understand how, because I do not need to mark the entire message, but only what is after the @ symbol.

This function is great for RolePlay, it is used in the / me / do commands and not only to explain which person is being accessed, for example, I have the ID 1A55 on the server and they contact me under my ID - / do How does it cost? @ 55