Only if one is a material square and the other is a spiritual square. You can't do two material or two spiritual of the same square because the squares have an exact amount to be done daily. No more, no less.
What Lanius said is right. But I would not do that. What has the highest chance of happening is you will make a mistake and end up messing up both squares. It is better to do one with twice the amount of focus and intention.