Open the same window when i push a button in a gtkwindow

Hi to all! A question for you........ I have a simple gtkwindow with a button. When i push the button I open a new gtkwindow. How can i to destroy or to hide this second gtkwindow when i click X ? And how can i reopen a new window when I push again the button? and how to prevent when a user click the button twice will be opened two different gtkwindow children? A piece of code could be useful Kind Regards Max