Hover your mouse over one of the tiles in XP. click on them, and near the bottom of the screen, to the right of the map name, there's two coordinates, the x and y coordinates. Move to the right, and the x coordinate increase, move left and it decreases. Move down, and the y variable increase, move up, and y variable decreases.
===>, x increases
<===, x decreases
down, y increases,
up, u decreases.
Simple.
Now, set the parrallel proccessing event to set player x/y coordinates in two different variables, and then constantly check x and/or y coordinates of the player in a conditional branch. Refer to the thingey above to know what coordinate is what. When the conditional branch is satisfied, when the player is below/above one variable, then activate the event(turn on a switch so you can turn the parrallel processing off), and so on so forth.