Identifying a selected text it anywhere Then copy to textbox Like babylon app

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C#

hi!
I'm doing a project
I need copy text a word with the click of a mouse anywhere (web_app_text...)Without my interference(by mouse position)

and move to mytextbox

like this :
Clipboard.SetText(richTextBox1.SelectedText);
Thread.Sleep(3000);

textBox1.Text = Clipboard.GetText();

but anywhere

tanks all