That is fine. You can change your pick as many times as you like, as long as the game you switch to hasn't started, and the game that you currently have picked isn't in progress or already over.
For example, if on sunday you have a late game picked, and the early games are already started, you can switch to another late game, or the monday game, but you can't switch to one of the early games or the thursday game.
See the week one thread starter for the whole explanation.--
Shine on you crazy diamond...