Hi, I don't have a problem with hosting any game, but what I want to do is be able to spectate every now and again

I used the following command in the console but it doesn't work, says unknown command in the chat window when I hit F4

bind "F4" "spectate"

Does anyone have an idea of what command I can use, so I can start hosting a game and then spectate?

Regards
CoNtEsA