Add command syntax highlight

First things first sorry about my poor english, i'm brazilian.

I was trying to create a command for my mod with some arguments like <target>, <action> and <value>, and i wish that this arguments are shown over the command text when typing it, like whether options are shown on /weather command, but i have no clue of how to do it.

I found some old topics about this, but none of then has a solution, so i think it was a good idea to bring this discussion back.

Edit: i just noticed that i put this topic on the wrong section, if any moderator can change it or delete this topic to i create a new one.