Script to disable crosshair when using lightsaber?

[CGameProgrammer]

I'm not really familiar with the Quake engine console commands. Can someone post a script/alias that disables the crosshair when using the lightsaber (or just when in third-person view, if that's easier) and enables it when using something else (or in first-person view)? And remind me how to enter and select it? Because I hate using the saber with a crosshair, but need it when using the guns.