Triggers Button IsFocused

Hello 

please i need your help

I have a 
TextBlock ==> Collapsed, 
button ==> Visible and 
  other controls ==> Visible 
  in a WPF application. . 
When I click the button, the TextBlock must be visible. 

I do not want to do it with c # (code behind) 
I just want to use XAML. 
so I writing this. 

<TextBlock FontSize="14" Text="{Binding description}" Width="400" Margin="28,5,0,0" TextWrapping="Wrap" Foreground="#FF1F1F1F" HorizontalAlignment="Left" FontWeight="Normal"   ><TextBlock.Style><Style TargetType="{x:Type TextBlock}"><Style.Triggers><DataTrigger Binding="{Binding ElementName=rMore, Path=IsFocused}" Value="true"><Setter Property="Visibility" Value="Collapsed"></Setter></DataTrigger><DataTrigger Binding="{Binding ElementName=rMore, Path=IsFocused}" Value="false"><Setter Property="Visibility" Value="Visible" ></Setter></DataTrigger></Style.Triggers></Style></TextBlock.Style></TextBlock>

  but when I click on another control my TextBlock disappears. 
How to keep the textblock always visible using the Triggers?

please using inly XAML.

Thanks in advance