How to Keep popup open when press enter key in textbox

Now I using a splitButton with some textbox in PopupGallery items.

Is therer any way to keep the popup open, when user finish typing and press enter key in these textboxs?

        <ribbon:SplitButton Click="..." >
        <ribbon:PopupGallery UseSingleColumn="True" ItemsSource="{Binding Path=...}" >
             <ribbon:PopupGallery.ItemTemplate>
                <DataTemplate>
                    <ribbon:TextBox Text ="{Binding Key, Mode=TwoWay}" />
                </DataTemplate>
              </ribbon:PopupGallery.ItemTemplate>
        </ribbon:PopupGallery>