[Outcast]

How to make it check if the player is on the right co-ordinates for a specific command? I mean, I know like for /enter command, how to check and all, but if there is 200 houses on the server, would I have to do 200 lines that check if the player is at the right entrance or a loop? Is there any other way to do it. Also, if I wanted to show a player a message when he steps infront of someone's door, would I have to do a loop and check it every time in OnPlayerUpdate (sounds a bit laggy to me). How to check a players position for a large number of positions, when he updates, but in an efficient way?