Oh, was too late - same idea, but I also have a second solutions so I post it anyway
I'm not sure if I understand you correctly
Do you mean you don't want player1 to cross to the other side?
If yes, I have two solutions
You can make an invisible border with a sprite block that can't be crossed. Or make a custom key movement for your player and give him a second condition (the following example subtracts half of the player x size - in this case 16 if the origin point is centered)
If pressed right
Player position.x <= windowwidth/2 - 16