Result in a window?

[floris]

I have tried to make a custom command, and I would like to see the result be displayed in a window (just like with the quote raw command which has an optional [x] display in window checkbox).

In the help it says, &window before the commands that follow, but when I do either:

&window command
command &window

they both return with 500 error. (something like &WINdow command not supported)

So how should I try and understand this option?

Thank you.