Probably 2 issues here. You can't change the player scheduled to pitch in the next game, and any tandem guys must be at the end of your rotation. What you'll need to do is wait until tandem 3 is due up, then switch 2 of your other guys to starters 1 and 2, while putting the other 2 on rest. The next game, Starter 1 will start, and you can then put everyone else in order as you want.
That's how I'd do it, anyway.