if BGGetDI(2) == 1 then
    
    -- check if the proximity sensor sees a backage close 
    -- if this is the case we can set a globabl varaible to 10 
    -- using the following command
    SetUserVal(uservar1,1);
    -- stop the conveyer belt
    BGSetDO(0,0)
end
if BGGetDI(2) == 0 then
    -- if the proximity sensor is 0 
    -- move the conveyer belt forward and update the global variable
    -- update it with small value maybe 1
    SetUserVal(uservar1,0);
    BGSetDO(0,1)
end