If you mean, as I suspect, that you want to drive one lamp during the day, and an different one at night, you probably could rig something up, but it would probably need manually triggering. If you got some new end caps for the second lamp, cut the end cap cables for the existing lamp and put a wafer or other type of changeover switch between the two pairs of ends and the starter, and you powered off and on after you changed the switch setting it might work, (just switching won't because the ballast won't "fire" the second lamp, it is at powerup it generates the "firing potential".
An electronic starter might well notice the lamp is not fired and fire again, but I don't know. They are so cheap these days, it's hardly worth the cost of the switch gear.
