NEED HELP WITH MACRO.

Hello. I am in need of how to create a macro that will send a message over a loop so I can go afk and it will continue to send a message on my browser. For example, if I press one macro hotkey and it toggles that message to send and loops. So like if I were to hot key F4, and it types out "hello" then sends that message. And continues to loop by itself so I do not have to press that hot key again.