[Norn]

pawn Code:

//top of script
new HMenuStarted[MAX_PLAYERS];
//OnPlayerConnect
HMenuStarted[playerid] = 0;

public OnPlayerPickUpPickup(playerid, pickupid)
{
  if(GetHouseID(playerid) != -255)
  {
    if(HMenuStarted[playerid] == 0)
    {
        TogglePlayerControllable(playerid, 0);
        ShowMenuForPlayer(EnterHousePickup, playerid);
        HMenuStarted[playerid] = 1;
        return 1;
    }
  }
  return 1;
}

Make sure to set HMenuStarted[playerid] to 0 when the player exits the menu.