Monitor Update For Redstone Input

So I've had a bit of an issue with getting a monitor that displays whether a redstone input is true or false. So for example, the monitor would display that a door is open, but flip the door switch(which is connected to the computer), and you would see the monitor change to say the door is closed. Sorry if this is kind of a noob question, but I'm just learning Lua

Here's a similar question, maybe you can use the program I posted there.