Check if button is clicked? Who can help correct command?

It doesn't work like that: What you denote as a hypothetical boolean property "clicked" of the class Button (I assume you mean System.Windows.Forms.Button) exists in form of an event named Click. Events aren't being read like a field or a property like in your theoretical code sample. They're being subscribed to and when they "fire" the method(s) that are subscribed to them ("event-handlers") are being called.

Try this:
- Open or create a project with a form.
- Open the form in the designer and place a button onto it.
- Double-click the button. Visual Studio automatically creates a method-stub (named "Button1_Click" if you didn't rename the button) and adds it to the subscriber-list of the Click-event of that button. Whenever the button is clicked that method will be called.
- Write the code that should be executed when the button is clicked into that method.

I strongly recommend you to find some books and/or good online tutorials. You're obviously a beginner and at that point you will learn faster and more thoroughly from a book or similar than asking in forums.