How can i stop my lip from shaking when i play the french horn in front of the whole band?

I just started playing the french horn in august last year and im slowly getting better...but only when im alone. In front of the whole band, not to mention my conductor, i get really nervous and afraid to mess up my solo on Dialogues by Michael Sweeney. Again, i can play the solo almost perfectly by myself, but with the band watching , my lip cant stop shaking and my solo comes out terribly. How can i stop this?