I had this working almost but I updated and forgot to keep a backup. But I had it so when they clicked a display name in the chat box. It put @@DisplayName in the textbox or input field. So you could just start typing after that. Useful if you have a lot of private PM's going back and forth.
But it didn't do it right. It would put say @@Bob in the box. Even though I clicked on Sally say in the chat box. So it wasn't grabbing the correct display name. I'll post my code here when I've got it back to wait it was.