so, after you score 37 points, it prompts you, not when you go over to try and buy a weapon?
i disaprove of that, as you could be in the middle of a battle
basicaly, i would put a zone on the roof and have it go downward, updating every 5 seconds or so (creating a new zone, so they enter it every 5 seconds), then onplayerenterzone, check if their score is >= the ammounts, if yes, check if a variable is not 1, if true, set it to 1, and prompt them, that way you don't prompt every 5 seconds, but only the first time after they get the score