What should I do for my Toolbar to work properly?

Hello folks,

I'm working on a script that I can use as a base and alter for different games and such. It basically creates a menu using GUI Buttons and such. A common button that will be in all of my works will be a options menu for changing the quality settings in-game.

This is my code so far: (The "GameSettings" If statement is so I can toggle the menu being visible or not. Just ignore that.)

 if(GameSettings==true) {
             string[] QualityNames=QualitySettings.names;
             int Setting = QualitySettings.GetQualityLevel ();
                 Setting = GUI.Toolbar (new Rect (230, 40, 500, 25), Setting, QualityNames);
 
         }

And so far it works to the point where it's displaying the default selected quality level OK, and it also is showing the correct number of options available. But now I'm stuck.

How do I check which button the user has selected and use this in an IF statement to both set the quality and do other things? (I intend to have GUI Labels appear to describe what the level of quality is, for instance telling the user the texture resolution and if shadows are enabled.)

Edit; Just so you're all aware, I'm doing this in C# - I'm not very well versed on it so I tend to ignore all the JavaScript people suggest as I don't know how I'd go about converting it.