如何将WPF窗口置于Excel VSTO插件中心

The problem is that a WPF window only takes a system.form.window so I cannot set Excel to be the owner object in my VSTO application, because the VSTO addin only exposes Excel's hwnd, or its active window as a Native Window since it is COM. That means when WindowStartUpLoadation is set to be center owner it doesn't work. So I am forced to work around this.The problem is that a WPF window only takes a s